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Leisgang N, Miserev D, Mattiat H, Schneider L, Sponfeldner L, Watanabe K, Taniguchi T, Poggio M, Warburton RJ. Exchange Energy of the Ferromagnetic Electronic Ground State in a Monolayer Semiconductor. PHYSICAL REVIEW LETTERS 2024; 133:026501. [PMID: 39073934 DOI: 10.1103/physrevlett.133.026501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 05/28/2024] [Indexed: 07/31/2024]
Abstract
Mobile electrons in the semiconductor monolayer MoS_{2} form a ferromagnetic state at low temperature. The Fermi sea consists of two circles: one at the K point, the other at the K[over ˜] point, both with the same spin. Here, we present an optical experiment on gated MoS_{2} at low electron density in which excitons are injected with known spin and valley quantum numbers. The resulting trions are identified using a model which accounts for the injection process, the formation of antisymmetrized trion states, electron-hole scattering from one valley to the other, and recombination. The results are consistent with a complete spin polarization. From the splittings between different trion states, we measure the exchange energy Σ, the energy required to flip a single spin within the ferromagnetic state, as well as the intervalley Coulomb exchange energy J. We determine Σ=11.2 meV and J=5 meV at n=1.5×10^{12} cm^{-2} and find that J depends strongly on the electron density n.
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2
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Sayer T, Farah YR, Austin R, Sambur J, Krummel AT, Montoya-Castillo A. Trion Formation Resolves Observed Peak Shifts in the Optical Spectra of Transition-Metal Dichalcogenides. NANO LETTERS 2023. [PMID: 37311112 DOI: 10.1021/acs.nanolett.3c01342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Monolayer transition-metal dichalcogenides (ML-TMDs) have the potential to unlock novel photonic and chemical technologies if their optoelectronic properties can be understood and controlled. Yet, recent work has offered contradictory explanations for how TMD absorption spectra change with carrier concentration, fluence, and time. Here, we test our hypothesis that the large broadening and shifting of the strong band-edge features observed in optical spectra arise from the formation of negative trions. We do this by fitting an ab initio based, many-body model to our experimental electrochemical data. Our approach provides an excellent, global description of the potential-dependent linear absorption data. We further leverage our model to demonstrate that trion formation explains the nonmonotonic potential dependence of the transient absorption spectra, including through photoinduced derivative line shapes for the trion peak. Our results motivate the continued development of theoretical methods to describe cutting-edge experiments in a physically transparent way.
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Affiliation(s)
- Thomas Sayer
- Department of Chemistry, University of Colorado Boulder, Boulder 80309, Colorado, United States
| | - Yusef R Farah
- Department of Chemistry, Colorado State University, Fort Collins 80523, Colorado, United States
| | - Rachelle Austin
- Department of Chemistry, Colorado State University, Fort Collins 80523, Colorado, United States
| | - Justin Sambur
- Department of Chemistry, Colorado State University, Fort Collins 80523, Colorado, United States
- School of Advanced Materials Discovery, Colorado State University, Fort Collins 80524, Colorado, United States
| | - Amber T Krummel
- Department of Chemistry, Colorado State University, Fort Collins 80523, Colorado, United States
| | - Andrés Montoya-Castillo
- Department of Chemistry, University of Colorado Boulder, Boulder 80309, Colorado, United States
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3
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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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4
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Covre FS, Faria PE, Gordo VO, de Brito CS, Zhumagulov YV, Teodoro MD, Couto ODD, Misoguti L, Pratavieira S, Andrade MB, Christianen PCM, Fabian J, Withers F, Galvão Gobato Y. Revealing the impact of strain in the optical properties of bubbles in monolayer MoSe 2. NANOSCALE 2022; 14:5758-5768. [PMID: 35348558 DOI: 10.1039/d2nr00315e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Strain plays an important role for the optical properties of monolayer transition metal dichalcogenides (TMDCs). Here, we investigate strain effects in a monolayer MoSe2 sample with a large bubble region using μ-Raman, second harmonic generation (SHG), μ-photoluminescence and magneto μ-photoluminescence at low temperature. Remarkably, our results reveal the presence of a non-uniform strain field and the observation of emission peaks at lower energies which are the signatures of exciton and trion quasiparticles red-shifted by strain effects in the bubble region, in agreement with our theoretical predictions. Furthermore, we have observed that the emission in the strained region decreases the trion binding energy and enhances the valley g-factors as compared to non-strained regions. Considering uniform biaxial strain effects within the unit cell of the TMDC monolayer (ML), our first principles calculations predict the observed enhancement of the exciton valley Zeeman effect. In addition, our results suggest that the exciton-trion fine structure plays an important role for the optical properties of strained TMDC ML. In summary, our study provides fundamental insights on the behaviour of excitons and trions in strained monolayer MoSe2 which are particularly relevant to properly characterize and understand the fine structure of excitonic complexes in strained TMDC systems/devices.
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Affiliation(s)
- F S Covre
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - P E Faria
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - V O Gordo
- Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859, Campinas, São Paulo, Brazil
| | - C Serati de Brito
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - Y V Zhumagulov
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M D Teodoro
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - O D D Couto
- Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859, Campinas, São Paulo, Brazil
| | - L Misoguti
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - S Pratavieira
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - M B Andrade
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - P C M Christianen
- High Field Magnet Laboratory (HFML - EMFL), Radboud University, 6525 ED Nijmegen, The Netherlands
| | - J Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - F Withers
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - Y Galvão Gobato
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
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5
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Lee J, Bang S, Park HJ, Park DY, Park C, Duong NT, Won YS, Jang J, Oh HM, Choi SH, Kim KK, Jeong MS. Interface Trap Suppression and Electron Doping in Van der Waals Materials Using Cross-Linked Poly(vinylpyrrolidone). ACS APPLIED MATERIALS & INTERFACES 2021; 13:55489-55497. [PMID: 34761893 DOI: 10.1021/acsami.1c12968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The instability of van der Waals (vdW) materials leads to spontaneous morphological and chemical transformations in the air. Although the passivation of vdW materials with other resistive materials is often used to solve stability issues, this passivation layer can block carrier injection and thus interfere with charge transfer doping. In this study, a facile method is proposed for n-doping and mediation of Se vacancies in tungsten diselenide (WSe2) by poly(vinylpyrrolidone) (PVP) coating. The major carrier type of the PVP-coated WSe2-based field-effect transistor (FET) was converted from hole (p-type) to electron (n-type). Furthermore, the vacancy-induced interface trap density was reduced by approximately 500 times. This study provides a practical doping and passivation method for the van der Waals materials, as well as a comprehensive understanding of the chemical reaction and electronic transport in these materials.
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Affiliation(s)
- Juchan Lee
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Seungho Bang
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Hyeon Jung Park
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
| | - Dae Young Park
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
| | - Chulho Park
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Ngoc Thanh Duong
- Department of Materials Science and Engineering, Phenikaa University, Hanoi 12116, Viet Nam
| | - Yo Seob Won
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Jiseong Jang
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Hye Min Oh
- Department of Physics, Kunsan National University, Kunsan 54150, Republic of Korea
| | - Soo Ho Choi
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science, Suwon 16419, Republic of Korea
| | - Ki Kang Kim
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science, Suwon 16419, Republic of Korea
| | - Mun Seok Jeong
- Department of Physics, Hanyang University (HYU), Seoul 04763, Republic of Korea
- Department of Energy Engineering, Hanyang University (HYU), Seoul 04763, Republic of Korea
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6
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Chang YW, Chang YC. Variationally optimized orbital approach to trions in two-dimensional materials. J Chem Phys 2021; 155:024110. [PMID: 34266270 DOI: 10.1063/5.0057493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work, trions in two-dimensional (2D) space are studied by the variational method with trial wavefunctions being constructed by 2D slater-type orbitals. Via this method, trion energy levels and wavefunctions can be calculated efficiently with fairly good accuracy. We first apply this method to study trion energy levels in a 2D hydrogen-like system with respect to a wide range of mass ratios and screening lengths. We find that the ground-state trion is bound for the whole parameter range, and an excited-state trion with antisymmetric permutation of electrons with finite angular momentum is bound for large electron-hole mass ratios or long screening lengths. The binding energies of ground-state trions calculated by the present method agree well with those calculated by more sophisticated but computationally demanding methods. We then calculate trion binding energies in various monolayer transition metal dichalcogenides (TMDCs) by using this method with the inclusion of electron-hole exchange (EHX) interaction. For TMDCs, we found that the effect of EHX can be significant in determining the trion binding energy and the possible existence of stable excited-state trions.
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Affiliation(s)
- Yao-Wen Chang
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Yia-Chung Chang
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
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7
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Brill AR, Kafri A, Mohapatra PK, Ismach A, de Ruiter G, Koren E. Modulating the Optoelectronic Properties of MoS 2 by Highly Oriented Dipole-Generating Monolayers. ACS APPLIED MATERIALS & INTERFACES 2021; 13:32590-32597. [PMID: 34190537 DOI: 10.1021/acsami.1c09035] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The noncovalent functionalization of two-dimensional materials (2DMs) with bespoke organic molecules is of central importance for future nanoscale electronic devices. Of particular interest is the incorporation of molecular functionalities that can modulate the physicochemical properties of the 2DMs via noninvasive external stimuli. In this study, we present the reversible modulation of the photoluminescence, spectroscopic properties (Raman), and charge transport characteristics of molybdenum disulfide (MoS2)-based devices via photoisomerization of a self-assembled monolayer of azobenzene-modified triazatriangulene molecules. The observed (opto)electronic modulations are explained by the n-type doping of the MoS2 lattice induced by the photoisomerization of the highly ordered azobenzene monolayer. This novel behavior could have profound effects on future composite 2DM-based (opto)electronics.
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Affiliation(s)
- Adam R Brill
- Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Technion City, Haifa 3200008, Israel
- Faculty of Materials Science and Engineering, Technion - Israel Institute of Technology, Technion City, Haifa 3200008, Israel
| | - Alonit Kafri
- Faculty of Materials Science and Engineering, Technion - Israel Institute of Technology, Technion City, Haifa 3200008, Israel
| | - Pranab K Mohapatra
- Department of Materials Science and Engineering, Tel Aviv University, Ramat Aviv, Tel Aviv 6997801, Israel
| | - Ariel Ismach
- Department of Materials Science and Engineering, Tel Aviv University, Ramat Aviv, Tel Aviv 6997801, Israel
| | - Graham de Ruiter
- Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Technion City, Haifa 3200008, Israel
| | - Elad Koren
- Faculty of Materials Science and Engineering, Technion - Israel Institute of Technology, Technion City, Haifa 3200008, Israel
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8
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Zalipaev VV, Kuidin VV. Semiclassical approach for excitonic spectrum of Coulomb coupling between two Dirac particles. Proc Math Phys Eng Sci 2021. [DOI: 10.1098/rspa.2021.0098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The properties of the energy spectrum of excitons in monolayer transition metal dichalcogenides are investigated using a multiband model. In the multiband model, we use the excitonic Hamiltonian in the product base of the Dirac single-particle states at the conduction and valence band edges. Following the separation of variables, we decouple the corresponding energy eigenvalue system of the first-order ODE radial equations rigorously and solve the resulting second-order ODE self-consistently, using the finite difference method, thus we determine the energy eigenvalues of the discrete excitonic spectrum and the corresponding wave functions. We also developed a WKB approach to solve the same spectral problem in semiclassical approximation for the resulting ODE. We compare the results for the energy spectrum and the corresponding eigen-function forms for WS
2
and WSe
2
obtained by means of both methods. We also compare our results for the energy spectrum with other theoretical works for excitons, and with available experimental data.
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9
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Affiliation(s)
- Xiaoyang Zhu
- 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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