1
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Xiang B, Wang R, Chen Y, Wang Y, Qin T, Zhang M, Watanabe K, Taniguchi T, Duan W, Tang P, Liu H, Xiong Q. Chirality-Dependent Dynamic Evolution for Trions in Monolayer WS 2. NANO LETTERS 2024; 24:6592-6600. [PMID: 38787539 DOI: 10.1021/acs.nanolett.4c01082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Monolayer transition metal dichalcogenides exhibit valley-dependent excitonic characters with a large binding energy, acting as the building block for future optoelectronic functionalities. Herein, combined with pump-probe ultrafast transient transmission spectroscopy and theoretical simulations, we reveal the chirality-dependent trion dynamics in h-BN encapsulated monolayer tungsten disulfide. By resonantly pumping trions in a single valley and monitoring their temporal evolution, we identify the temperature-dependent competition between two relaxation channels driven by chirality-dependent scattering processes. At room temperature, the phonon-assisted upconversion process predominates, converting excited trions to excitons within the same valley on a sub-picosecond (ps) time scale. As temperature decreases, this process becomes less efficient, while alternative channels, notably valley depolarization process for trions, assume importance, leading to an increase of trion density in the unpumped valley within a ps time scale. Our time-resolved valley-contrast results provide a comprehensive insight into trion dynamics in 2D materials, thereby advancing the development of novel valleytronic devices.
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Affiliation(s)
- Baixu Xiang
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Renqi Wang
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
| | - Yuzhong Chen
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Yubin Wang
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Tingxiao Qin
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Mengdi Zhang
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Wenhui Duan
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Institute for Advanced Study, Tsinghua University, Beijing 100084, P. R. China
- Frontier Science Center for Quantum Information, Beijing, 100084, P. R. China
| | - Peizhe Tang
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - Haiyun Liu
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Qihua Xiong
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
- Frontier Science Center for Quantum Information, Beijing, 100084, P. R. China
- Collaborative Innovation Center of Quantum Matter, Beijing, 100084, P.R. China
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2
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Tatarczak P, Iwański J, Dąbrowska AK, Tokarczyk M, Binder J, Stępniewski R, Wysmołek A. Strain modulation of epitaxial h-BN on sapphire: the role of wrinkle formation for large-area two-dimensional materials. NANOTECHNOLOGY 2024; 35:175703. [PMID: 38150722 DOI: 10.1088/1361-6528/ad18e6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 12/27/2023] [Indexed: 12/29/2023]
Abstract
Strain built-in electronic and optoelectronic devices can influence their properties and lifetime. This effect is particularly significant at the interface between two-dimensional materials and substrates. One such material is epitaxial hexagonal boron nitride (h-BN), which is grown at temperatures often exceeding 1000 °C. Due to the high growth temperature, h-BN based devices operating at room temperature can be strongly affected by strain generated during cooling due to the differences in lattice thermal expansion of h-BN and the substrate. Here, we present results of temperature-dependent Raman studies of the in-plane E2ghighphonon mode in the temperature range of 300-1100 K measured for h-BN grown by metalorganic vapor phase epitaxy. We observe a change, by an order of magnitude, in the rate of the temperature-induced frequency shift for temperatures below 900 K, indicating a strong reduction of the effective h-BN/substrate interaction. We attribute this behavior to the creation of h-BN wrinkles which results in strain relaxation. This interpretation is supported by the observation that no change of layer/substrate interaction and no wrinkles are observed for delaminated h-BN films transferred onto silicon. Our findings demonstrate that wrinkle formation is an inherent process for two-dimensional materials on foreign substrates that has to be understood to allow for the successful engineering of devices based on epitaxially grown van der Waals heterostructures.
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Affiliation(s)
- Piotr Tatarczak
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Jakub Iwański
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | | | - Mateusz Tokarczyk
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Johannes Binder
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Roman Stępniewski
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Andrzej Wysmołek
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
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3
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Adler ER, Le TDM, Boulares I, Boyd R, He Y, Rhodes D, Van Keuren E, Barbara P, Najmaei S. Observation of Multi-Phonon Emission in Monolayer WS 2 on Various Substrates. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 14:37. [PMID: 38202492 PMCID: PMC10780943 DOI: 10.3390/nano14010037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/14/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024]
Abstract
Transition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin-orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering processes remains elusive. In tungsten-based TMDs, it is known that the excitons formed from electrons in the lower-energy conduction bands are dark in nature, whereas low-energy emissions in the photoluminescence spectrum have been linked to the brightening of these transitions, either via defect scattering or via phonon scattering with first-order phonon replicas. Through temperature and incident-power-dependent studies of WS2 grown by CVD or exfoliated from high-purity bulk crystal on different substrates, we demonstrate that the strong exciton-phonon coupling yields brightening of dark transitions up to sixth-order phonon replicas. We discuss the critical role of defects in the brightening pathways of dark excitons and their phonon replicas, and we elucidate that these emissions are intrinsic to the material and independent of substrate, encapsulation, growth method, and transfer approach.
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Affiliation(s)
- Eli R. Adler
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USA
| | - Thy Doan Mai Le
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
| | - Ibrahim Boulares
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USA
| | - Robert Boyd
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Yangchen He
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Daniel Rhodes
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Edward Van Keuren
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
| | - Paola Barbara
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
| | - Sina Najmaei
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USA
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4
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Jadczak J, Debus J, Olejnik J, Ho CH, Watanabe K, Taniguchi T, Bryja L. Biexciton and Singlet Trion Upconvert Exciton Photoluminescence in a MoSe 2 Monolayer Supported by Acoustic and Optical K-Valley Phonons. J Phys Chem Lett 2023; 14:8702-8708. [PMID: 37733953 PMCID: PMC10561254 DOI: 10.1021/acs.jpclett.3c01982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 09/18/2023] [Indexed: 09/23/2023]
Abstract
Transition metal dichalcogenide monolayers represent unique platforms for studying both electronic and phononic interactions as well as intra- and intervalley exciton complexes. Here, we investigate the upconversion of exciton photoluminescence in MoSe2 monolayers. Within the nominal transparency window of MoSe2 the exciton emission is enhanced for resonantly addressing the spin-singlet negative trion and neutral biexciton at a few tens of meV below the neutral exciton transition. We identify that the A'1 optical phonon at the K valley provides the energy gain in the upconversion process at the trion resonance, while ZA(K) phonons with their spin- and valley-switching properties support the biexciton driven upconversion of the exciton emission. Interestingly, the latter upconversion process yields unpolarized exciton photoluminescence, while the former also leads to circularly polarized emission. Our study highlights high-order exciton complexes interacting with optical and acoustic K-valley phonons and upconverting light into the bright exciton.
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Affiliation(s)
- Joanna Jadczak
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Joerg Debus
- Department
of Physics, TU Dortmund University, 44227 Dortmund, Germany
| | - Justyna Olejnik
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Ching-Hwa Ho
- Graduate
Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan
| | - Kenji Watanabe
- National
Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- National
Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Leszek Bryja
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
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5
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Zhumagulov YV, Vagov A, Gulevich DR, Perebeinos V. Electrostatic and Environmental Control of the Trion Fine Structure in Transition Metal Dichalcogenide Monolayers. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3728. [PMID: 36364505 PMCID: PMC9656490 DOI: 10.3390/nano12213728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
Charged excitons or trions are essential for optical spectra in low-dimensional doped monolayers (ML) of transitional metal dichalcogenides (TMDC). Using a direct diagonalization of the three-body Hamiltonian, we calculate the low-lying trion states in four types of TMDC MLs as a function of doping and dielectric environment. We show that the fine structure of the trion is the result of the interplay between the spin-valley fine structure of the single-particle bands and the exchange interaction. We demonstrate that by variations of the doping and dielectric environment, the fine structure of the trion energy can be tuned, leading to anticrossing of the bright and dark states, with substantial implications for the optical spectra of the TMDC ML.
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Affiliation(s)
| | - Alexei Vagov
- Faculty of Physics, National Research University Higher School of Economics, 101000 Moscow, Russia
| | | | - Vasili Perebeinos
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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6
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Interactions between Fermi polarons in monolayer WS 2. Nat Commun 2022; 13:6164. [PMID: 36257945 PMCID: PMC9579159 DOI: 10.1038/s41467-022-33811-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 10/04/2022] [Indexed: 11/23/2022] Open
Abstract
Interactions between quasiparticles are of fundamental importance and ultimately determine the macroscopic properties of quantum matter. A famous example is the phenomenon of superconductivity, which arises from attractive electron-electron interactions that are mediated by phonons or even other more exotic fluctuations in the material. Here we introduce mobile exciton impurities into a two-dimensional electron gas and investigate the interactions between the resulting Fermi polaron quasiparticles. We employ multi-dimensional coherent spectroscopy on monolayer WS2, which provides an ideal platform for determining the nature of polaron-polaron interactions due to the underlying trion fine structure and the valley specific optical selection rules. At low electron doping densities, we find that the dominant interactions are between polaron states that are dressed by the same Fermi sea. In the absence of bound polaron pairs (bipolarons), we show using a minimal microscopic model that these interactions originate from a phase-space filling effect, where excitons compete for the same electrons. We furthermore reveal the existence of a bipolaron bound state with remarkably large binding energy, involving excitons in different valleys cooperatively bound to the same electron. Our work lays the foundation for probing and understanding strong electron correlation effects in two-dimensional layered structures such as moiré superlattices. Here, the authors investigate the interactions between Fermi polarons in monolayer WS2 by multi-dimensional coherent spectroscopy, and find that, at low electron doping densities, the dominant interactions are between polaron states that are dressed by the same Fermi sea. They also observe a bipolaron bound state with large binding energy, involving excitons in different valleys cooperatively bound to the same electron.
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7
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Żuberek E, Majak M, Lubczyński J, Debus J, Watanabe K, Taniguchi T, Ho CH, Bryja L, Jadczak J. Upconversion photoluminescence excitation reveals exciton-trion and exciton-biexciton coupling in hBN/WS[Formula: see text]/hBN van der Waals heterostructures. Sci Rep 2022; 12:13699. [PMID: 35953508 PMCID: PMC9372078 DOI: 10.1038/s41598-022-18104-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 08/05/2022] [Indexed: 11/10/2022] Open
Abstract
Monolayers of transition-metal dichalcogenides with direct band gap located at the binary [Formula: see text] points of the Brillouin zone are promising materials for applications in opto- and spin-electronics due to strongly enhanced Coulomb interactions and specific spin-valley properties. They furthermore represent a unique platform to study electron-electron and electron-phonon interactions in diverse exciton complexes. Here, we demonstrate processes in which the neutral biexciton and two negative trions, namely the spin-triplet and spin-singlet trions, upconvert light into a bright intravalley exciton in an hBN-encapsulated WS[Formula: see text] monolayer. We propose that the energy gains required in the polarized upconversion photoluminescence originate from different interactions including resonant optical phonons, a cooling of resident electrons and a non-local and an anisotropic electron-hole exchange, respectively. The temperature dependence (7-120 K) of the excitonic upconversion intensity obtained at excitation energies corresponding to the biexciton and trions provides insight into an increasing phonon population as well as a thermally enhanced electron scattering. Our study sheds new light on the understanding of excitonic spin and valley properties of van der Waals heterostructures and improves the understanding of photonic upconversion mechanisms in two-dimensional quantum materials.
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Affiliation(s)
- Ewa Żuberek
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Martyna Majak
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Jakub Lubczyński
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Joerg Debus
- Department of Physics, TU Dortmund University, 44227 Dortmund, Germany
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 Japan
| | - Ching-Hwa Ho
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 106 Taiwan
| | - Leszek Bryja
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Joanna Jadczak
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
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8
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Bieniek M, Sadecka K, Szulakowska L, Hawrylak P. Theory of Excitons in Atomically Thin Semiconductors: Tight-Binding Approach. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:1582. [PMID: 35564291 PMCID: PMC9104105 DOI: 10.3390/nano12091582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/24/2022] [Accepted: 04/26/2022] [Indexed: 02/01/2023]
Abstract
Atomically thin semiconductors from the transition metal dichalcogenide family are materials in which the optical response is dominated by strongly bound excitonic complexes. Here, we present a theory of excitons in two-dimensional semiconductors using a tight-binding model of the electronic structure. In the first part, we review extensive literature on 2D van der Waals materials, with particular focus on their optical response from both experimental and theoretical points of view. In the second part, we discuss our ab initio calculations of the electronic structure of MoS2, representative of a wide class of materials, and review our minimal tight-binding model, which reproduces low-energy physics around the Fermi level and, at the same time, allows for the understanding of their electronic structure. Next, we describe how electron-hole pair excitations from the mean-field-level ground state are constructed. The electron-electron interactions mix the electron-hole pair excitations, resulting in excitonic wave functions and energies obtained by solving the Bethe-Salpeter equation. This is enabled by the efficient computation of the Coulomb matrix elements optimized for two-dimensional crystals. Next, we discuss non-local screening in various geometries usually used in experiments. We conclude with a discussion of the fine structure and excited excitonic spectra. In particular, we discuss the effect of band nesting on the exciton fine structure; Coulomb interactions; and the topology of the wave functions, screening and dielectric environment. Finally, we follow by adding another layer and discuss excitons in heterostructures built from two-dimensional semiconductors.
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Affiliation(s)
- Maciej Bieniek
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
- Department of Theoretical Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
| | - Katarzyna Sadecka
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
- Department of Theoretical Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Ludmiła Szulakowska
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
| | - Paweł Hawrylak
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
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9
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Huang L, Krasnok A, Alú A, Yu Y, Neshev D, Miroshnichenko AE. Enhanced light-matter interaction in two-dimensional transition metal dichalcogenides. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2022; 85:046401. [PMID: 34939940 DOI: 10.1088/1361-6633/ac45f9] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 12/16/2021] [Indexed: 05/27/2023]
Abstract
Two-dimensional (2D) transition metal dichalcogenide (TMDC) materials, such as MoS2, WS2, MoSe2, and WSe2, have received extensive attention in the past decade due to their extraordinary electronic, optical and thermal properties. They evolve from indirect bandgap semiconductors to direct bandgap semiconductors while their layer number is reduced from a few layers to a monolayer limit. Consequently, there is strong photoluminescence in a monolayer (1L) TMDC due to the large quantum yield. Moreover, such monolayer semiconductors have two other exciting properties: large binding energy of excitons and valley polarization. These properties make them become ideal materials for various electronic, photonic and optoelectronic devices. However, their performance is limited by the relatively weak light-matter interactions due to their atomically thin form factor. Resonant nanophotonic structures provide a viable way to address this issue and enhance light-matter interactions in 2D TMDCs. Here, we provide an overview of this research area, showcasing relevant applications, including exotic light emission, absorption and scattering features. We start by overviewing the concept of excitons in 1L-TMDC and the fundamental theory of cavity-enhanced emission, followed by a discussion on the recent progress of enhanced light emission, strong coupling and valleytronics. The atomically thin nature of 1L-TMDC enables a broad range of ways to tune its electric and optical properties. Thus, we continue by reviewing advances in TMDC-based tunable photonic devices. Next, we survey the recent progress in enhanced light absorption over narrow and broad bandwidths using 1L or few-layer TMDCs, and their applications for photovoltaics and photodetectors. We also review recent efforts of engineering light scattering, e.g., inducing Fano resonances, wavefront engineering in 1L or few-layer TMDCs by either integrating resonant structures, such as plasmonic/Mie resonant metasurfaces, or directly patterning monolayer/few layers TMDCs. We then overview the intriguing physical properties of different van der Waals heterostructures, and their applications in optoelectronic and photonic devices. Finally, we draw our opinion on potential opportunities and challenges in this rapidly developing field of research.
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Affiliation(s)
- Lujun Huang
- School of Engineering and Information Technology, University of New South Wales, Canberra, ACT, 2600, Australia
| | - Alex Krasnok
- Department of Electrical and Computer Engineering, Florida International University, Miami, FL 33174, United States of America
| | - Andrea Alú
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY 10031, United States of America
- Physics Program, Graduate Center, City University of New York, New York, NY 10016, United States of America
| | - Yiling Yu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States of America
| | - Dragomir Neshev
- ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - Andrey E Miroshnichenko
- School of Engineering and Information Technology, University of New South Wales, Canberra, ACT, 2600, Australia
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10
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Li J, Goryca M, Choi J, Xu X, Crooker SA. Many-Body Exciton and Intervalley Correlations in Heavily Electron-Doped WSe 2 Monolayers. NANO LETTERS 2022; 22:426-432. [PMID: 34918936 DOI: 10.1021/acs.nanolett.1c04217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In monolayer transition-metal dichalcogenide semiconductors, many-body correlations can manifest in optical spectra when electron-hole pairs (excitons) are photoexcited into a 2D Fermi sea of mobile carriers. At low carrier densities, the formation of charged excitons (X±) is well documented. However, in WSe2 monolayers, an additional absorption resonance, often called X-', emerges at high electron density. Its origin is not understood. Here, we investigate the X-' state via polarized absorption spectroscopy of gated WSe2 monolayers in magnetic fields to 60T. Field-induced filling and emptying of the lowest optically active Landau level in the K' valley causes repeated quenching of the corresponding optical absorption. Surprisingly, these quenchings are accompanied by absorption changes to higher Landau levels in both K' and K valleys, which are unoccupied. These results cannot be reconciled within a single-particle picture, and demonstrate the many-body nature and intervalley correlations of the X-' quasiparticle state.
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Affiliation(s)
- Jing Li
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Hubei 430074, China
| | - Mateusz Goryca
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Junho Choi
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Scott A Crooker
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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11
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Jadczak J, Glazov M, Kutrowska-Girzycka J, Schindler JJ, Debus J, Ho CH, Watanabe K, Taniguchi T, Bayer M, Bryja L. Upconversion of Light into Bright Intravalley Excitons via Dark Intervalley Excitons in hBN-Encapsulated WSe 2 Monolayers. ACS NANO 2021; 15:19165-19174. [PMID: 34735768 PMCID: PMC8717626 DOI: 10.1021/acsnano.1c08286] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 10/29/2021] [Indexed: 05/19/2023]
Abstract
Semiconducting monolayers of transition-metal dichalcogenides are outstanding platforms to study both electronic and phononic interactions as well as intra- and intervalley excitons and trions. These excitonic complexes are optically either active (bright) or inactive (dark) due to selection rules from spin or momentum conservation. Exploring ways of brightening dark excitons and trions has strongly been pursued in semiconductor physics. Here, we report on a mechanism in which a dark intervalley exciton upconverts light into a bright intravalley exciton in hBN-encapsulated WSe2 monolayers. Excitation spectra of upconverted photoluminescence reveals resonances at energies 34.5 and 46.0 meV below the neutral exciton in the nominal WSe2 transparency range. The required energy gains are theoretically explained by cooling of resident electrons or by exciton scattering with Λ- or K-valley phonons. Accordingly, an elevated temperature and a moderate concentration of resident electrons are necessary for observing the upconversion resonances. The interaction process observed between the inter- and intravalley excitons elucidates the importance of dark excitons for the optics of two-dimensional materials.
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Affiliation(s)
- Joanna Jadczak
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
- (J.J.)
| | | | - Joanna Kutrowska-Girzycka
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | | | - Joerg Debus
- Experimental
Physics 2, TU Dortmund University, 44227 Dortmund, Germany
| | - Ching-Hwa Ho
- Graduate
Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan
| | - Kenji Watanabe
- National
Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- National
Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Manfred Bayer
- Experimental
Physics 2, TU Dortmund University, 44227 Dortmund, Germany
| | - Leszek Bryja
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
- (L.B.)
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12
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Grzeszczyk M, Olkowska-Pucko K, Nogajewski K, Watanabe K, Taniguchi T, Kossacki P, Babiński A, Molas MR. Exposing the trion's fine structure by controlling the carrier concentration in hBN-encapsulated MoS 2. NANOSCALE 2021; 13:18726-18733. [PMID: 34739017 DOI: 10.1039/d1nr03855a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Atomically thin materials, like semiconducting transition metal dichalcogenides, are highly sensitive to the environment. This opens up an opportunity to externally control their properties by changing their surroundings. In this work, high-quality van der Waals heterostructures assembled from hBN-encapsulated monolayer MoS2 are studied with the aid of photoluminescence, photoluminescence excitation, and reflectance contrast experiments. We demonstrate that carrier concentration in MoS2 monolayers, arising from charge transfer from impurities in the substrate, can be significantly tuned within one order of magnitude by the modification of the bottom hBN flake thickness. The studied structures, characterized by spectral lines with linewidths approaching the narrow homogeneously broadened limit enabled observations of subtle optical and spin-valley properties of excitonic complexes. Our results allowed us to resolve three optically-active negatively charged excitons in MoS2 monolayers, which are assigned to the intravalley singlet, intervalley singlet, and intervalley triplet states.
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Affiliation(s)
- Magdalena Grzeszczyk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Katarzyna Olkowska-Pucko
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Karol Nogajewski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 305-0044, Japan
| | - Piotr Kossacki
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Adam Babiński
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Maciej R Molas
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
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13
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Robert C, Park S, Cadiz F, Lombez L, Ren L, Tornatzky H, Rowe A, Paget D, Sirotti F, Yang M, Van Tuan D, Taniguchi T, Urbaszek B, Watanabe K, Amand T, Dery H, Marie X. Spin/valley pumping of resident electrons in WSe 2 and WS 2 monolayers. Nat Commun 2021; 12:5455. [PMID: 34526493 PMCID: PMC8443707 DOI: 10.1038/s41467-021-25747-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 08/31/2021] [Indexed: 11/09/2022] Open
Abstract
Monolayers of transition metal dichalcogenides are ideal materials to control both spin and valley degrees of freedom either electrically or optically. Nevertheless, optical excitation mostly generates excitons species with inherently short lifetime and spin/valley relaxation time. Here we demonstrate a very efficient spin/valley optical pumping of resident electrons in n-doped WSe2 and WS2 monolayers. We observe that, using a continuous wave laser and appropriate doping and excitation densities, negative trion doublet lines exhibit circular polarization of opposite sign and the photoluminescence intensity of the triplet trion is more than four times larger with circular excitation than with linear excitation. We interpret our results as a consequence of a large dynamic polarization of resident electrons using circular light.
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Affiliation(s)
- Cedric Robert
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077, Toulouse, France.
| | - Sangjun Park
- Physique de la matière condensée, Ecole Polytechnique, CNRS, IP Paris, 91128, Paris, Palaiseau, France
| | - Fabian Cadiz
- Physique de la matière condensée, Ecole Polytechnique, CNRS, IP Paris, 91128, Paris, Palaiseau, France.
| | - Laurent Lombez
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077, Toulouse, France
| | - Lei Ren
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077, Toulouse, France
| | - Hans Tornatzky
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077, Toulouse, France
| | - Alistair Rowe
- Physique de la matière condensée, Ecole Polytechnique, CNRS, IP Paris, 91128, Paris, Palaiseau, France
| | - Daniel Paget
- Physique de la matière condensée, Ecole Polytechnique, CNRS, IP Paris, 91128, Paris, Palaiseau, France
| | - Fausto Sirotti
- Physique de la matière condensée, Ecole Polytechnique, CNRS, IP Paris, 91128, Paris, Palaiseau, France
| | - Min Yang
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - Dinh Van Tuan
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-00044, Japan
| | - Bernhard Urbaszek
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077, Toulouse, France
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-00044, Japan
| | - Thierry Amand
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077, Toulouse, France
| | - Hanan Dery
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY, 14627, USA
- Department of Physics, University of Rochester, Rochester, NY, 14627, USA
| | - Xavier Marie
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077, Toulouse, France.
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14
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Zinkiewicz M, Woźniak T, Kazimierczuk T, Kapuscinski P, Oreszczuk K, Grzeszczyk M, Bartoš M, Nogajewski K, Watanabe K, Taniguchi T, Faugeras C, Kossacki P, Potemski M, Babiński A, Molas MR. Excitonic Complexes in n-Doped WS 2 Monolayer. NANO LETTERS 2021; 21:2519-2525. [PMID: 33683895 PMCID: PMC7995249 DOI: 10.1021/acs.nanolett.0c05021] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/22/2021] [Indexed: 05/25/2023]
Abstract
We investigate the origin of emission lines apparent in the low-temperature photoluminescence spectra of n-doped WS2 monolayer embedded in hexagonal BN layers using external magnetic fields and first-principles calculations. Apart from the neutral A exciton line, all observed emission lines are related to the negatively charged excitons. Consequently, we identify emissions due to both the bright (singlet and triplet) and dark (spin- and momentum-forbidden) negative trions as well as the phonon replicas of the latter optically inactive complexes. The semidark trions and negative biexcitons are distinguished. On the basis of their experimentally extracted and theoretically calculated g-factors, we identify three distinct families of emissions due to exciton complexes in WS2: bright, intravalley, and intervalley dark. The g-factors of the spin-split subbands in both the conduction and valence bands are also determined.
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Affiliation(s)
- Małgorzata Zinkiewicz
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Tomasz Woźniak
- Department
of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego
27, 50-370 Wrocław, Poland
| | - Tomasz Kazimierczuk
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Piotr Kapuscinski
- Laboratoire
National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France
- Department
of Experimental Physics, Wrocław University
of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wrocław, Poland
| | - Kacper Oreszczuk
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Magdalena Grzeszczyk
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Miroslav Bartoš
- Laboratoire
National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France
- Central
European Institute of Technology, Brno University
of Technology, Purkyňova
656/123, 612 00 Brno, Czech Republic
| | - Karol Nogajewski
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Clement Faugeras
- Laboratoire
National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France
| | - Piotr Kossacki
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Marek Potemski
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
- Laboratoire
National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France
| | - Adam Babiński
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - Maciej R. Molas
- Institute
of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
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15
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Hotta T, Ueda A, Higuchi S, Okada M, Shimizu T, Kubo T, Ueno K, Taniguchi T, Watanabe K, Kitaura R. Enhanced Exciton-Exciton Collisions in an Ultraflat Monolayer MoSe 2 Prepared through Deterministic Flattening. ACS NANO 2021; 15:1370-1377. [PMID: 33356145 DOI: 10.1021/acsnano.0c08642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Squeezing bubbles and impurities out of interlayer spaces by applying force through a few-layer graphene capping layer leads to van der Waals heterostructures with the ultraflat structure free from random electrostatic potential arising from charged impurities. Without the graphene capping layer, a squeezing process with an AFM tip induces applied-force-dependent charges of Δn ∼ 2 × 1012 cm-2 μN-1, resulting in the significant intensity of trions in photoluminescence spectra of MoSe2 at low temperature. We found that a hBN/MoSe2/hBN prepared with the "graphene-capping-assisted AFM nano-squeezing method" shows a strong excitonic emission with negligible trion peak, and the residual line width of the exciton peak is only 2.2 meV, which is comparable to the homogeneous limit. Furthermore, in this high-quality sample, we found that the formation of biexciton occurs even at extremely low excitation power (Φph ∼ 2.3 × 1019 cm-2 s-1) due to the enhanced collisions between excitons.
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Affiliation(s)
- Takato Hotta
- Department of Chemistry, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - Akihiko Ueda
- Department of Chemistry, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - Shohei Higuchi
- Department of Chemistry, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - Mitsuhiro Okada
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan
| | - Tetsuo Shimizu
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan
| | - Toshitaka Kubo
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan
| | - Keiji Ueno
- Department of Chemistry, Saitama University, Saitama 338-8570, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Ryo Kitaura
- Department of Chemistry, Nagoya University, Nagoya, Aichi 464-8602, Japan
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16
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Jadczak J, Kutrowska-Girzycka J, Bieniek M, Kazimierczuk T, Kossacki P, Schindler JJ, Debus J, Watanabe K, Taniguchi T, Ho CH, Wójs A, Hawrylak P, Bryja L. Probing negatively charged and neutral excitons in MoS 2/hBN and hBN/MoS 2/hBN van der Waals heterostructures. NANOTECHNOLOGY 2021; 32:145717. [PMID: 33463532 DOI: 10.1088/1361-6528/abd507] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
High-quality van der Waals heterostructures assembled from hBN-encapsulated monolayer transition metal dichalcogenides enable observations of subtle optical and spin-valley properties whose identification was beyond the reach of structures exfoliated directly on standard SiO2/Si substrates. Here, we describe different van der Waals heterostructures based on uncapped single-layer MoS2 stacked onto hBN layers of different thicknesses and hBN-encapsulated monolayers. Depending on the doping level, they reveal the fine structure of excitonic complexes, i.e. neutral and charged excitons. In the emission spectra of a particular MoS2/hBN heterostructure without an hBN cap we resolve two trion peaks, T1 and T2, energetically split by about 10 meV, resembling the pair of singlet and triplet trion peaks (T S and T T ) in tungsten-based materials. The existence of these trion features suggests that monolayer MoS2 has a dark excitonic ground state, despite having a 'bright' single-particle arrangement of spin-polarized conduction bands. In addition, we show that the effective excitonic g-factor significantly depends on the electron concentration and reaches the lowest value of -2.47 for hBN-encapsulated structures, which reveals a nearly neutral doping regime. In the uncapped MoS2 structures, the excitonic g-factor varies from -1.15 to -1.39 depending on the thickness of the bottom hBN layer and decreases as a function of rising temperature.
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Affiliation(s)
- J Jadczak
- Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
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17
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Investigations of Electron-Electron and Interlayer Electron-Phonon Coupling in van der Waals hBN/WSe 2/hBN Heterostructures by Photoluminescence Excitation Experiments. MATERIALS 2021; 14:ma14020399. [PMID: 33467435 PMCID: PMC7830124 DOI: 10.3390/ma14020399] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 01/10/2021] [Accepted: 01/11/2021] [Indexed: 11/17/2022]
Abstract
Monolayers of transition metal dichalcogenides (TMDs) with their unique physical properties are very promising for future applications in novel electronic devices. In TMDs monolayers, strong and opposite spin splittings of the energy gaps at the K points allow for exciting carriers with various combinations of valley and spin indices using circularly polarized light, which can further be used in spintronics and valleytronics. The physical properties of van der Waals heterostructures composed of TMDs monolayers and hexagonal boron nitride (hBN) layers significantly depend on different kinds of interactions. Here, we report on observing both a strong increase in the emission intensity as well as a preservation of the helicity of the excitation light in the emission from hBN/WSe2/hBN heterostructures related to interlayer electron-phonon coupling. In combined low-temperature (T = 7 K) reflectivity contrast and photoluminescence excitation experiments, we find that the increase in the emission intensity is attributed to a double resonance, where the laser excitation and the combined Raman mode A'1 (WSe2) + ZO (hBN) are in resonance with the excited (2s) and ground (1s) states of the A exciton in a WSe2 monolayer. In reference to the 2s state, our interpretation is in contrast with previous reports, in which this state has been attributed to the hybrid exciton state existing only in the hBN-encapsulated WSe2 monolayer. Moreover, we observe that the electron-phonon coupling also enhances the helicity preservation of the exciting light in the emission of all observed excitonic complexes. The highest helicity preservation of more than 60% is obtained in the emission of the neutral biexciton and negatively charged exciton (trion) in its triplet state. Additionally, to the best of our knowledge, the strongly intensified emission of the neutral biexciton XX0 at double resonance condition is observed for the first time.
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18
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Wagner K, Wietek E, Ziegler JD, Semina MA, Taniguchi T, Watanabe K, Zipfel J, Glazov MM, Chernikov A. Autoionization and Dressing of Excited Excitons by Free Carriers in Monolayer WSe_{2}. PHYSICAL REVIEW LETTERS 2020; 125:267401. [PMID: 33449708 DOI: 10.1103/physrevlett.125.267401] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 11/09/2020] [Indexed: 06/12/2023]
Abstract
We experimentally demonstrate dressing of the excited exciton states by a continuously tunable Fermi sea of free charge carriers in a monolayer semiconductor. It represents an unusual scenario of two-particle excitations of charged excitons previously inaccessible in conventional material systems. We identify excited state trions, accurately determine their binding energies in the zero-density limit for both electron- and hole-doped regimes, and observe emerging many-body phenomena at elevated doping. Combining experiment and theory we gain access to the intra-exciton coupling facilitated by the interaction with free charge carriers. We provide evidence for a process of autoionization for quasiparticles, a unique scattering pathway available for excited states in atomic systems. Finally, we demonstrate a complete transfer of the optical transition strength from the excited excitons to dressed Fermi-polaron states as well as the associated light emission from their nonequilibrium populations.
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Affiliation(s)
- Koloman Wagner
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Edith Wietek
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Jonas D Ziegler
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | | | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | | | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
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19
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Zinkiewicz M, Slobodeniuk AO, Kazimierczuk T, Kapuściński P, Oreszczuk K, Grzeszczyk M, Bartos M, Nogajewski K, Watanabe K, Taniguchi T, Faugeras C, Kossacki P, Potemski M, Babiński A, Molas MR. Neutral and charged dark excitons in monolayer WS 2. NANOSCALE 2020; 12:18153-18159. [PMID: 32853305 DOI: 10.1039/d0nr04243a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Low temperature and polarization resolved magneto-photoluminescence experiments are used to investigate the properties of dark excitons and dark trions in a monolayer of WS2 encapsulated in hexagonal BN (hBN). We find that this system is an n-type doped semiconductor and that dark trions dominate the emission spectrum. In line with previous studies on WSe2, we identify the Coulomb exchange interaction coupled neutral dark and grey excitons through their polarization properties, while an analogous effect is not observed for dark trions. Applying the magnetic field in both perpendicular and parallel configurations with respect to the monolayer plane, we determine the g-factor of dark trions to be g ∼ -8.6. Their decay rate is close to 0.5 ns, more than 2 orders of magnitude longer than that of bright excitons.
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Affiliation(s)
- M Zinkiewicz
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
| | - A O Slobodeniuk
- Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, Praha 2 CZ-121 16, Czech Republic
| | - T Kazimierczuk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
| | - P Kapuściński
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France and Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, ul. Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - K Oreszczuk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
| | - M Grzeszczyk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
| | - M Bartos
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France and Central European Institute of Technology, Brno University of Technology, Purkyňova 656/123, 612 00 Brno, Czech Republic
| | - K Nogajewski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - C Faugeras
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France
| | - P Kossacki
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
| | - M Potemski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland. and Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042 Grenoble, France
| | - A Babiński
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
| | - M R Molas
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland.
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20
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Goldstein T, Wu YC, Chen SY, Taniguchi T, Watanabe K, Varga K, Yan J. Ground and excited state exciton polarons in monolayer MoSe 2. J Chem Phys 2020; 153:071101. [PMID: 32828093 DOI: 10.1063/5.0013092] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Monolayer transition metal dichalcogenide semiconductors, with versatile experimentally accessible exciton species, offer an interesting platform for investigating the interaction between excitons and a Fermi sea of charges. Using hexagonal boron nitride encapsulated monolayer MoSe2, we study the impact of charge density tuning on the A and B series of exciton Rydberg states, including A:1s, A:2s, B:1s, and B:2s. The doping dependence of the A:2s state provides an opportunity to examine such interactions with greatly reduced exciton binding energy and more spatially diffuse structures, and we found that the impact of the Fermi sea becomes much more dramatic compared to the A:1s state. Using photoluminescence upconversion, we verify that the B:2s exciton state displays similar behavior when interacting with the Fermi sea despite being well above the bare bandgap in energy. Photoluminescence and reflection spectra of the A:1s state show clear evidence that the interaction of the exciton with a Fermi sea is best described by the exciton-polaron model, rather than a trion model. Our experimental results demonstrate that overall features of charge interaction are quite generic and highly robust, offering key insights into the dressed many body states in a Fermi sea.
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Affiliation(s)
- Thomas Goldstein
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Yueh-Chun Wu
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Shao-Yu Chen
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Kalman Varga
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Jun Yan
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
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21
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Zipfel J, Wagner K, Ziegler JD, Taniguchi T, Watanabe K, Semina MA, Chernikov A. Light-matter coupling and non-equilibrium dynamics of exchange-split trions in monolayer WS 2. J Chem Phys 2020; 153:034706. [PMID: 32716167 DOI: 10.1063/5.0012721] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Monolayers of transition metal dichalcogenides present an intriguing platform to investigate the interplay of excitonic complexes in two-dimensional semiconductors. Here, we use optical spectroscopy to study the light-matter coupling and non-equilibrium relaxation dynamics of three-particle exciton states, commonly known as trions. We identify the consequences of the exchange interaction for the trion fine structure in tungsten-based monolayer materials from variational calculations and experimentally determine the resulting characteristic differences in their oscillator strength. It allows us to quantitatively extract trion populations from time-resolved photoluminescence measurements and monitor their dynamics after off-resonant optical injection. At liquid helium temperature, we observe a pronounced non-equilibrium distribution of the trions during their lifetime with comparatively slow equilibration that occurs on time-scales up to several hundreds of ps. In addition, we find an intriguing regime of population inversion at lowest excitation densities, which builds up and is maintained for tens of picoseconds. At a higher lattice temperature, the equilibrium is established more rapidly and the inversion disappears, highlighting the role of thermal activation for efficient scattering between exchange-split trions.
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Affiliation(s)
- Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - Koloman Wagner
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - Jonas D Ziegler
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | | | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg, Germany
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22
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Lorchat E, López LEP, Robert C, Lagarde D, Froehlicher G, Taniguchi T, Watanabe K, Marie X, Berciaud S. Filtering the photoluminescence spectra of atomically thin semiconductors with graphene. NATURE NANOTECHNOLOGY 2020; 15:283-288. [PMID: 32152557 DOI: 10.1038/s41565-020-0644-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 01/20/2020] [Indexed: 06/10/2023]
Abstract
Atomically thin semiconductors made from transition metal dichalcogenides (TMDs) are model systems for investigations of strong light-matter interactions and applications in nanophotonics, optoelectronics and valleytronics. However, the photoluminescence spectra of TMD monolayers display a large number of features that are particularly challenging to decipher. On a practical level, monochromatic TMD-based emitters would be beneficial for low-dimensional devices, but this challenge is yet to be resolved. Here, we show that graphene, directly stacked onto TMD monolayers, enables single and narrow-line photoluminescence arising solely from TMD neutral excitons. This filtering effect stems from complete neutralization of the TMD by graphene, combined with selective non-radiative transfer of long-lived excitonic species to graphene. Our approach is applied to four tungsten- and molybdenum-based TMDs and establishes TMD/graphene heterostructures as a unique set of optoelectronic building blocks that are suitable for electroluminescent systems emitting visible and near-infrared photons at near THz rate with linewidths approaching the homogeneous limit.
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Affiliation(s)
- Etienne Lorchat
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Strasbourg, France
| | - Luis E Parra López
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Strasbourg, France
| | - Cédric Robert
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, Toulouse, France
| | | | - Guillaume Froehlicher
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Strasbourg, France
| | | | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki, Japan
| | - Xavier Marie
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, Toulouse, France
- Institut Universitaire de France, Paris, France
| | - Stéphane Berciaud
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Strasbourg, France.
- Institut Universitaire de France, Paris, France.
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23
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Kapuściński P, Vaclavkova D, Grzeszczyk M, Slobodeniuk AO, Nogajewski K, Bartos M, Watanabe K, Taniguchi T, Faugeras C, Babiński A, Potemski M, Molas MR. Valley polarization of singlet and triplet trions in a WS2 monolayer in magnetic fields. Phys Chem Chem Phys 2020; 22:19155-19161. [DOI: 10.1039/d0cp02737e] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Magnetic field induced valley polarization of carriers is substantially different for the absorption and emission response of a WS2 monolayer.
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24
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Liu Y, Hu X, Wang T, Liu D. Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS 2. ACS NANO 2019; 13:14416-14425. [PMID: 31825594 DOI: 10.1021/acsnano.9b08004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The exciton dynamics in WS2 from monolayer to four-layer was investigated by using fluorescence lifetime imaging measurement (FLIM). The transition process of negatively charged trions is measured and detected using a fluorescence detection method. Compared with neutral excitons, negatively charged trions have a longer fluorescence lifetime. Further exploration illustrated that the fluorescence lifetime of both neutral excitons and trions get longer when the thickness increased. When WS2 was added from monolayer to four-layer, lifetimes of direct transition excitons and trions tended to increase over 10 and 2.5 times, separately, whereas the lifetime of indirect transition excitons tended to be reduced by nearly 2.5 times. This layer-dependent signature is ascribed to the reduced binding energy in thicker WS2 at room temperature, which is verified by density theory functional calculation. Although the direct transition exciton dominates the whole fluorescence decay process, it is influenced by trions and dark excitons. Based on the FLIM results, we proposed four main exciton transition channels during the fluorescence luminescence process. Such layer-dependent transition channel conception helps to control the fluorescence lifetime, which determines the efficiency of the carriers' separation.
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Affiliation(s)
- Yuanshuang Liu
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Xiangmin Hu
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Ting Wang
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Dameng Liu
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
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25
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Arora A, Deilmann T, Reichenauer T, Kern J, Michaelis de Vasconcellos S, Rohlfing M, Bratschitsch R. Excited-State Trions in Monolayer WS_{2}. PHYSICAL REVIEW LETTERS 2019; 123:167401. [PMID: 31702327 DOI: 10.1103/physrevlett.123.167401] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Indexed: 05/16/2023]
Abstract
We discover an excited bound three-particle state, the 2s trion, appearing energetically below the 2s exciton in monolayer WS_{2}, using absorption spectroscopy and ab initio GW and Bethe-Salpeter equation calculations. The measured binding energy of the 2s trion (22 meV) is smaller compared to the 1s intravalley and intervalley trions (37 and 31 meV). With increasing temperature, the 1s and 2s trions transfer their oscillator strengths to the respective neutral excitons, establishing an optical fingerprint of trion-exciton resonance pairs. Our discovery underlines the importance of trions for the entire excitation spectrum of two-dimensional semiconductors.
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Affiliation(s)
- Ashish Arora
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
| | - Thorsten Deilmann
- Institute of Solid State Theory, Wilhelm-Klemm-Straße 10, University of Münster, 48149 Münster, Germany
| | - Till Reichenauer
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
| | - Johannes Kern
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
| | | | - Michael Rohlfing
- Institute of Solid State Theory, Wilhelm-Klemm-Straße 10, University of Münster, 48149 Münster, Germany
| | - Rudolf Bratschitsch
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
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26
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Molas MR, Slobodeniuk AO, Nogajewski K, Bartos M, Bala Ł, Babiński A, Watanabe K, Taniguchi T, Faugeras C, Potemski M. Energy Spectrum of Two-Dimensional Excitons in a Nonuniform Dielectric Medium. PHYSICAL REVIEW LETTERS 2019; 123:136801. [PMID: 31697524 DOI: 10.1103/physrevlett.123.136801] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate that, in monolayers (MLs) of semiconducting transition metal dichalcogenides, the s-type Rydberg series of excitonic states follows a simple energy ladder: ε_{n}=-Ry^{*}/(n+δ)^{2}, n=1,2,…, in which Ry^{*} is very close to the Rydberg energy scaled by the dielectric constant of the medium surrounding the ML and by the reduced effective electron-hole mass, whereas the ML polarizability is accounted for only by δ. This is justified by the analysis of experimental data on excitonic resonances, as extracted from magneto-optical measurements of a high-quality WSe_{2} ML encapsulated in hexagonal boron nitride (hBN), and well reproduced with an analytically solvable Schrödinger equation when approximating the electron-hole potential in the form of a modified Kratzer potential. Applying our convention to other MoSe_{2}, WS_{2}, MoS_{2} MLs encapsulated in hBN, we estimate an apparent magnitude of δ for each of the studied structures. Intriguingly, δ is found to be close to zero for WSe_{2} as well as for MoS_{2} monolayers, what implies that the energy ladder of excitonic states in these two-dimensional structures resembles that of Rydberg states of a three-dimensional hydrogen atom.
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Affiliation(s)
- M R Molas
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - A O Slobodeniuk
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
| | - K Nogajewski
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - M Bartos
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Central European Institute of Technology, Brno University of Technology, Purkyňova 656/123, 61200 Brno, Czech Republic
| | - Ł Bala
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - A Babiński
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - C Faugeras
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
| | - M Potemski
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
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27
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Molas MR, Slobodeniuk AO, Kazimierczuk T, Nogajewski K, Bartos M, Kapuściński P, Oreszczuk K, Watanabe K, Taniguchi T, Faugeras C, Kossacki P, Basko DM, Potemski M. Probing and Manipulating Valley Coherence of Dark Excitons in Monolayer WSe_{2}. PHYSICAL REVIEW LETTERS 2019; 123:096803. [PMID: 31524465 DOI: 10.1103/physrevlett.123.096803] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Indexed: 06/10/2023]
Abstract
Monolayers of semiconducting transition metal dichalcogenides are two-dimensional direct-gap systems which host tightly bound excitons with an internal degree of freedom corresponding to the valley of the constituting carriers. Strong spin-orbit interaction and the resulting ordering of the spin-split subbands in the valence and conduction bands makes the lowest-lying excitons in WX_{2} (X being S or Se) spin forbidden and optically dark. With polarization-resolved photoluminescence experiments performed on a WSe_{2} monolayer encapsulated in a hexagonal boron nitride, we show how the intrinsic exchange interaction in combination with the applied in-plane and/or out-of-plane magnetic fields enables one to probe and manipulate the valley degree of freedom of the dark excitons.
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Affiliation(s)
- M R Molas
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - A O Slobodeniuk
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
| | - T Kazimierczuk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - K Nogajewski
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - M Bartos
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
| | - P Kapuściński
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, 27 Wybrzeże Wyspiańskiego, 50-370 Wrocław, Poland
| | - K Oreszczuk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - C Faugeras
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
| | - P Kossacki
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
| | - D M Basko
- Laboratoire de Physique et Modélisation des Milieux Condensés, Université Grenoble Alpes and CNRS, 25 avenue des Martyrs, 38042 Grenoble, France
| | - M Potemski
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 avenue des Martyrs, 38042 Grenoble, France
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warszawa, Poland
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28
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Murali K, Abraham N, Das S, Kallatt S, Majumdar K. Highly Sensitive, Fast Graphene Photodetector with Responsivity >10 6 A/W Using a Floating Quantum Well Gate. ACS APPLIED MATERIALS & INTERFACES 2019; 11:30010-30018. [PMID: 31347352 DOI: 10.1021/acsami.9b06835] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Graphene, owing to its zero-band-gap electronic structure, is promising as an absorption material for ultra-wideband photodetection applications. However, graphene-absorption-based detectors inherently suffer from poor responsivity because of weak absorption and fast photocarrier recombination, limiting their viability for low-intensity light detection. Here, we use a graphene/WS2/MoS2 vertical heterojunction to demonstrate a highly sensitive photodetector, where the graphene layer serves dual purposes, namely, as the light absorption layer and also as the carrier conduction channel, thus maintaining the broadband nature of the photodetector. A fraction of the photoelectrons in graphene encounter ultrafast interlayer transfer to a floating monolayer MoS2 quantum well, providing a strong quantum-confined photogating effect. The photodetector shows a responsivity of 4.4 × 106 A/W at 30 fW incident power, outperforming photodetectors reported till date where graphene is used as a light absorption material by several orders. In addition, the proposed photodetector exhibits an extremely low noise equivalent power of <4 fW/ Hz and a fast response (∼milliseconds) with zero reminiscent photocurrent. The findings are attractive toward the demonstration of a graphene-based highly sensitive, fast, broadband photodetection technology.
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Affiliation(s)
- Krishna Murali
- Department of Electrical Communication Engineering , Indian Institute of Science , Bangalore 560012 , India
| | - Nithin Abraham
- Department of Electrical Communication Engineering , Indian Institute of Science , Bangalore 560012 , India
| | - Sarthak Das
- Department of Electrical Communication Engineering , Indian Institute of Science , Bangalore 560012 , India
| | - Sangeeth Kallatt
- Department of Electrical Communication Engineering , Indian Institute of Science , Bangalore 560012 , India
| | - Kausik Majumdar
- Department of Electrical Communication Engineering , Indian Institute of Science , Bangalore 560012 , India
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29
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Fan P, Zheng B, Sun X, Zheng W, Xu Z, Ge C, Liu Y, Zhuang X, Li D, Wang X, Zhu X, Jiang Y, Pan A. Trion-Induced Distinct Transient Behavior and Stokes Shift in WS 2 Monolayers. J Phys Chem Lett 2019; 10:3763-3772. [PMID: 31244271 DOI: 10.1021/acs.jpclett.9b01422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Understanding the excitonic behavior in two-dimensional transition-metal dichalcogenides (2D TMDs) is of both fundamental interest and critical importance for optoelectronic applications. Here, we investigate the transient excitonic behavior and Stokes shift in WS2 monolayers on both sapphire and glass substrates. Trion formation was confirmed as the origin of the distinct photoluminescence (PL) emission and Stokes shift in WS2 monolayers. Moreover, the transient studies demonstrate faster recombination of both the exciton and the short-lived trion on the glass substrate as compared to that on the sapphire substrate, owing to the heavier n-doping and greater number of defects introduced by the glass substrate. In addition, a long-lived trion species attributed to the intervalley triplet trion was observed on the glass substrate, with a lifetime on the nanosecond time scale. These findings offer a comprehensive understanding of the excitonic behavior and Stokes shift in WS2 monolayers and will lay the foundation for further fundamental investigations in the field.
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Affiliation(s)
- Peng Fan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Biyuan Zheng
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Xingxia Sun
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering , Hunan University , Changsha 410082 , People's Republic of China
| | - Weihao Zheng
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Zheyuan Xu
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Cuihuan Ge
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Yong Liu
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Xiujuan Zhuang
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Dong Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering , Hunan University , Changsha 410082 , People's Republic of China
| | - Xiao Wang
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Xiaoli Zhu
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Ying Jiang
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronics , Hunan University , Changsha 410082 , People's Republic of China
| | - Anlian Pan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering , Hunan University , Changsha 410082 , People's Republic of China
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30
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The valley Zeeman effect in inter- and intra-valley trions in monolayer WSe 2. Nat Commun 2019; 10:2330. [PMID: 31133703 PMCID: PMC6536528 DOI: 10.1038/s41467-019-10228-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 04/29/2019] [Indexed: 11/27/2022] Open
Abstract
Monolayer transition metal dichalcogenides (TMDs) hold great promise for future information processing applications utilizing a combination of electron spin and valley pseudospin. This unique spin system has led to observation of the valley Zeeman effect in neutral and charged excitonic resonances under applied magnetic fields. However, reported values of the trion valley Zeeman splitting remain highly inconsistent across studies. Here, we utilize high quality hBN encapsulated monolayer WSe2 to enable simultaneous measurement of both intervalley and intravalley trion photoluminescence. We find the valley Zeeman splitting of each trion state to be describable only by a combination of three distinct g-factors, one arising from the exciton-like valley Zeeman effect, the other two, trion specific, g-factors associated with recoil of the excess electron. This complex picture goes significantly beyond the valley Zeeman effect reported for neutral excitons, and eliminates the ambiguity surrounding the magneto-optical response of trions in tungsten based TMD monolayers. The unique valley and spin texture of atomically thin transition metal dichalcogenides (TMDs) allows the observation of the valley Zeeman effect for neutral and charged excitons. Here, the authors unveil the underlying physics of the magneto-optical response and valley Zeeman splitting of trions in tungsten-based TMDs.
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31
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Molas MR, Gołasa K, Bala Ł, Nogajewski K, Bartos M, Potemski M, Babiński A. Tuning carrier concentration in a superacid treated MoS 2 monolayer. Sci Rep 2019; 9:1989. [PMID: 30760791 PMCID: PMC6374480 DOI: 10.1038/s41598-018-38413-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 12/27/2018] [Indexed: 11/25/2022] Open
Abstract
The effect of bis(trifluoromethane) sulfonimide (TFSI, superacid) treatment on the optical properties of MoS2 monolayers is investigated by means of photoluminescence, reflectance contrast and Raman scattering spectroscopy employed in a broad temperature range. It is shown that when applied multiple times, the treatment results in progressive quenching of the trion emission/absorption and in the redshift of the neutral exciton emission/absorption associated with both the A and B excitonic resonances. Based on this evolution, a trion complex related to the B exciton in monolayer MoS2 is unambiguously identified. A defect-related emission observed at low temperatures also disappears from the spectrum as a result of the treatment. Our observations are attributed to effective passivation of defects on the MoS2 monolayer surface. The passivation reduces the carrier density, which in turn affects the out-of-plane electric field in the sample. The observed tuning of the carrier concentration strongly influences also the Raman scattering in the MoS2 monolayer. An enhancement of Raman scattering at resonant excitation in the vicinity of the A neutral exciton is clearly seen for both the out-of-plane A′1 and in-plane E′ modes. On the contrary, when the excitation is in resonance with a corresponding trion, the Raman scattering features become hardly visible. These results confirm the role of the excitonic charge state plays in the resonance effect of the excitation energy on the Raman scattering in transition metal dichalcogenides.
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Affiliation(s)
- Maciej R Molas
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland. .,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France.
| | - Katarzyna Gołasa
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland
| | - Łukasz Bala
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France
| | - Karol Nogajewski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France
| | - Miroslav Bartos
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland
| | - Marek Potemski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.,Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25, avenue des Martyrs, 38042, Grenoble, France
| | - Adam Babiński
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093, Warszawa, Poland.
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32
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Wang X, Hossain M, Wei Z, Xie L. Growth of two-dimensional materials on hexagonal boron nitride (h-BN). NANOTECHNOLOGY 2019; 30:034003. [PMID: 30444726 DOI: 10.1088/1361-6528/aaeb70] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
With its atomically smooth surface yet no dangling bond, chemical inertness and high temperature sustainability, the insulating hexagonal boron nitride (h-BN) can be an ideal substrate for two-dimensional (2D) material growth and device measurement. In this review, research progress on the chemical growth of 2D materials on h-BN has been summarized, such as chemical vapor deposition and molecular beam epitaxy of graphene and various transition metal dichalcogenides. Further, stacking of the as-grown 2D materials relative to h-BN, thermal expansion matching between the deposited materials and h-BN, electrical property of 2D materials on h-BN have been discussed in detail.
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Affiliation(s)
- Xinsheng Wang
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
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