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Pasquale G, Sun Z, Čerņevičs K, Perea-Causin R, Tagarelli F, Watanabe K, Taniguchi T, Malic E, Yazyev OV, Kis A. Flat-Band-Induced Many-Body Interactions and Exciton Complexes in a Layered Semiconductor. NANO LETTERS 2022; 22:8883-8891. [PMID: 36346874 PMCID: PMC9707521 DOI: 10.1021/acs.nanolett.2c02965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 10/31/2022] [Indexed: 06/16/2023]
Abstract
Interactions among a collection of particles generate many-body effects in solids that result in striking modifications of material properties. The heavy carrier mass that yields strong interactions and gate control of carrier density over a wide range makes two-dimensional semiconductors an exciting playground to explore many-body physics. The family of III-VI metal monochalcogenides emerges as a new platform for this purpose because of its excellent optical properties and the flat valence band dispersion. In this work, we present a complete study of charge-tunable excitons in few-layer InSe by photoluminescence spectroscopy. From the optical spectra, we establish that free excitons in InSe are more likely to be captured by ionized donors leading to the formation of bound exciton complexes. Surprisingly, a pronounced red shift of the exciton energy accompanied by a decrease of the exciton binding energy upon hole-doping reveals a significant band gap renormalization induced by the presence of the Fermi reservoir.
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Affiliation(s)
- Gabriele Pasquale
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
| | - Zhe Sun
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
| | - Kristia̅ns Čerņevičs
- Institute
of Physics, École Polytechnique Fédérale
de Lausanne (EPFL), CH-1015Lausanne, Switzerland
| | - Raul Perea-Causin
- Chalmers
University of Technology, Department of Physics, 412
96Gothenburg, Sweden
| | - Fedele Tagarelli
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | - Ermin Malic
- Philipps-Universität
Marburg, Department of Physics, Renthof 7, D-35032Marburg, Germany
- Chalmers
University of Technology, Department of Physics, 412
96Gothenburg, Sweden
| | - Oleg V. Yazyev
- Institute
of Physics, École Polytechnique Fédérale
de Lausanne (EPFL), CH-1015Lausanne, Switzerland
| | - Andras Kis
- Institute
of Electrical and Microengineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
- Institute
of Materials Science and Engineering, École
Polytechnique Fédérale de Lausanne (EPFL), CH-1015Lausanne, Switzerland
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2
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Van Tuan D, Shi SF, Xu X, Crooker SA, Dery H. Six-Body and Eight-Body Exciton States in Monolayer WSe_{2}. PHYSICAL REVIEW LETTERS 2022; 129:076801. [PMID: 36018693 DOI: 10.1103/physrevlett.129.076801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 07/08/2022] [Indexed: 06/15/2023]
Abstract
In the archetypal monolayer semiconductor WSe_{2}, the distinct ordering of spin-polarized valleys (low-energy pockets) in the conduction band allows for studies of not only simple neutral excitons and charged excitons (i.e., trions), but also more complex many-body states that are predicted at higher electron densities. We discuss magneto-optical measurements of electron-rich WSe_{2} monolayers and interpret the spectral lines that emerge at high electron doping as optical transitions of six-body exciton states ("hexcitons") and eight-body exciton states ("oxcitons"). These many-body states emerge when a photoexcited electron-hole pair interacts simultaneously with multiple Fermi seas, each having distinguishable spin and valley quantum numbers. In addition, we explain the relations between dark trions and satellite optical transitions of hexcitons in the photoluminescence spectrum.
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Affiliation(s)
- Dinh Van Tuan
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA
| | - Su-Fei Shi
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
- Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, USA
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA
| | - Scott A Crooker
- National High Magnetic Field Laboratory, Los Alamos, New Mexico 87545, USA
| | - Hanan Dery
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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3
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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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4
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Robert C, Dery H, Ren L, Van Tuan D, Courtade E, Yang M, Urbaszek B, Lagarde D, Watanabe K, Taniguchi T, Amand T, Marie X. Measurement of Conduction and Valence Bands g-Factors in a Transition Metal Dichalcogenide Monolayer. PHYSICAL REVIEW LETTERS 2021; 126:067403. [PMID: 33635701 DOI: 10.1103/physrevlett.126.067403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 12/03/2020] [Indexed: 06/12/2023]
Abstract
The electron valley and spin degree of freedom in monolayer transition-metal dichalcogenides can be manipulated in optical and transport measurements performed in magnetic fields. The key parameter for determining the Zeeman splitting, namely, the separate contribution of the electron and hole g factor, is inaccessible in most measurements. Here we present an original method that gives access to the respective contribution of the conduction and valence band to the measured Zeeman splitting. It exploits the optical selection rules of exciton complexes, in particular the ones involving intervalley phonons, avoiding strong renormalization effects that compromise single particle g-factor determination in transport experiments. These studies yield a direct determination of single band g factors. We measure g_{c1}=0.86±0.1, g_{c2}=3.84±0.1 for the bottom (top) conduction bands and g_{v}=6.1±0.1 for the valence band of monolayer WSe_{2}. These measurements are helpful for quantitative interpretation of optical and transport measurements performed in magnetic fields. In addition, the measured g factors are valuable input parameters for optimizing band structure calculations of these 2D materials.
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Affiliation(s)
- C Robert
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - H Dery
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA
- Department of Physics, University of Rochester, Rochester, New York 14627, USA
| | - L Ren
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - D Van Tuan
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA
| | - E Courtade
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - M Yang
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA
| | - B Urbaszek
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - D Lagarde
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - T Amand
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - X Marie
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France
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Xu G, Zhou T, Scharf B, Žutić I. Optically Probing Tunable Band Topology in Atomic Monolayers. PHYSICAL REVIEW LETTERS 2020; 125:157402. [PMID: 33095598 DOI: 10.1103/physrevlett.125.157402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 06/26/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
In many atomically thin materials, their optical absorption is dominated by excitonic transitions. It was recently found that optical selection rules in these materials are influenced by the band topology near the valleys. We propose that gate-controlled band ordering in a single atomic monolayer, through changes in the valley winding number and excitonic transitions, can be probed in helicity-resolved absorption and photoluminescence. This predicted tunable band topology is confirmed by combining an effective Hamiltonian and a Bethe-Salpeter equation for an accurate description of excitons, with first-principles calculations suggesting its realization in Sb-based monolayers.
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Affiliation(s)
- Gaofeng Xu
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Tong Zhou
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Benedikt Scharf
- Institute for Theoretical Physics and Astrophysics and Würzburg-Dresden Cluster of Excellence ct.qmat, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Igor Žutić
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
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Zhumagulov YV, Vagov A, Gulevich DR, Faria Junior PE, Perebeinos V. Trion induced photoluminescence of a doped MoS2 monolayer. J Chem Phys 2020; 153:044132. [DOI: 10.1063/5.0012971] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Yaroslav V. Zhumagulov
- ITMO University, St. Petersburg 197101, Russia
- University of Regensburg, Regensburg 93040, Germany
| | | | | | | | - Vasili Perebeinos
- ITMO University, St. Petersburg 197101, Russia
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA
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7
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Joshi J, Zhou T, Krylyuk S, Davydov AV, Zutic I, Vora PM. Localized Excitons in NbSe 2-MoSe 2 Heterostructures. ACS NANO 2020; 14:8528-8538. [PMID: 32639717 PMCID: PMC8171581 DOI: 10.1021/acsnano.0c02803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Neutral and charged excitons (trions) in atomically thin materials offer important capabilities for photonics, from ultrafast photodetectors to highly efficient light-emitting diodes and lasers. Recent studies of van der Waals (vdW) heterostructures comprised of dissimilar monolayer materials have uncovered a wealth of optical phenomena that are predominantly governed by interlayer interactions. Here, we examine the optical properties in NbSe2-MoSe2 vdW heterostructures, which provide an important model system to study metal-semiconductor interfaces, a common element in optoelectronics. Through low-temperature photoluminescence (PL) microscopy, we discover a sharp emission feature, L1, that is localized at the NbSe2-capped regions of MoSe2. L1 is observed at energies below the commonly studied MoSe2 excitons and trions and exhibits temperature- and power-dependent PL consistent with exciton localization in a confining potential. This PL feature is robust, observed in a variety of samples fabricated with different stacking geometries and cleaning procedures. Using first-principles calculations, we reveal that the confinement potential required for exciton localization naturally arises from the in-plane band bending due to the changes in the electron affinity between pristine MoSe2 and NbSe2-MoSe2 heterostructure. We discuss the implications of our studies for atomically thin optoelectronics devices with atomically sharp interfaces and tunable electronic structures.
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Affiliation(s)
- Jaydeep Joshi
- Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030, United States
- Quantum Science and Engineering Center, George Mason University, Fairfax, Virginia 22030, United States
| | - Tong Zhou
- Department of Physics, University at Buffalo, Buffalo, New York 14260, United States
| | - Sergiy Krylyuk
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Albert V. Davydov
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Igor Zutic
- Department of Physics, University at Buffalo, Buffalo, New York 14260, United States
| | - Patrick M. Vora
- Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030, United States
- Quantum Science and Engineering Center, George Mason University, Fairfax, Virginia 22030, United States
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8
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Carbone MR, Mayers MZ, Reichman DR. Microscopic model of the doping dependence of linewidths in monolayer transition metal dichalcogenides. J Chem Phys 2020; 152:194705. [PMID: 33687247 DOI: 10.1063/5.0008730] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A fully microscopic model of the doping-dependent exciton and trion linewidths in the absorption spectra of monolayer transition metal dichalcogenides in the low temperature and low-doping regime is explored. The approach is based on perturbation theory and avoids the use of phenomenological parameters. In the low-doping regime, we find that the trion linewidth is relatively insensitive to doping levels, while the exciton linewidth increases monotonically with doping. On the other hand, we argue that the trion linewidth shows a somewhat stronger temperature dependence. The magnitudes of the linewidths are likely to be masked by phonon scattering for T ≥ 20 K in encapsulated samples in the low-doping regime. We discuss the breakdown of perturbation theory, which should occur at relatively low-doping levels and low temperatures. Our work also paves the way toward understanding a variety of related scattering processes, including impact ionization and Auger scattering in clean 2D samples.
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Affiliation(s)
- Matthew R Carbone
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Matthew Z Mayers
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - David R Reichman
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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Zhang J, Huang GQ. The superconductivity and topological surface state of type-II Dirac semimetal NiTe 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:205702. [PMID: 31978915 DOI: 10.1088/1361-648x/ab6f84] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
NiTe2 is a type-II Dirac semimetal with the Dirac point very close to the Fermi level. In this paper, its electronic structure, phonon structure and electron-phonon interaction are studied via first-principles calculations. The noteworthy result is that the nontrival bands around the type-II Dirac point are strongly coupled with phonon modes, suggesting that they play an important role in superconductivity. Furthermore, the topological surface states on the (0 0 1) cleavage plane originated from the nontrivial Z 2 are well separated from the bulk states and can be tuned to approach the Fermi level by adding holes or by V substitution. The possible topological superconductivity in type-II Dirac semimetal NiTe2 is discussed.
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Affiliation(s)
- Jie Zhang
- Department of Physics, Nanjing Normal University, Nanjing 210023, People's Republic of China
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Electrostatic Interaction of Point Charges in Three-Layer Structures: The Classical Model. CONDENSED MATTER 2019. [DOI: 10.3390/condmat4020044] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Electrostatic interaction energy W between two point charges in a three-layer plane system was calculated on the basis of the Green’s function method in the classical model of constant dielectric permittivities for all media involved. A regular method for the calculation of W ( Z , Z ′ , R ) , where Z and Z ′ are the charge coordinates normal to the interfaces, and R the lateral (along the interfaces) distance between the charges, was proposed. The method consists in substituting the evaluation of integrals of rapidly oscillating functions over the semi-infinite interval by constructing an analytical series of inverse radical functions to a required accuracy. Simple finite-term analytical approximations of the dependence W ( Z , Z ′ , R ) were proposed. Two especially important particular cases of charge configurations were analyzed in more detail: (i) both charges are in the same medium and Z = Z ′ ; and (ii) the charges are located at different interfaces across the slab. It was demonstrated that the W dependence on the charge–charge distance S = R 2 + Z − Z ′ 2 differs from the classical Coulombic one W ∼ S − 1 . This phenomenon occurs due to the appearance of polarization charges at both interfaces, which ascribes a many-body character to the problem from the outset. The results obtained testify, in particular, that the electron–hole interaction in heterostructures leading to the exciton formation is different in the intra-slab and across-slab charge configurations, which is usually overlooked in specific calculations related to the subject concerned. Our consideration clearly demonstrates the origin, the character, and the consequences of the actual difference. The often used Rytova–Keldysh approximation was analyzed. The cause of its relative success was explained, and the applicability limits were determined.
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