1
|
Sun X, Lu Z, Lu Y. Enhanced interactions of excitonic complexes in free-standing WS 2. NANOSCALE 2023. [PMID: 37937449 DOI: 10.1039/d3nr04594c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
Excitonic complexes, bound states of electrons and holes, provide a promising platform in monolayer transition-metal dichalcogenide (TMDC) semiconductors for investigating diverse many-body interaction phenomena. The surrounding dielectric environment has been found to strongly influence the excitonic properties of the TMDC monolayers. While the impact of different dielectric surroundings on two-dimensional semiconductor materials and their strong correlations have been well studied, the effects on exciton formation and its properties resulting from a further reduction in dielectric screening remain elusive. In this study, we examined free-standing tungsten disulfide (WS2) monolayers, where the efficient generation of higher-order correlated excitonic complexes is readily observed. This phenomenon arises from the effective mutual interactions among excitons and internal carriers, attributed to the modulated exciton dynamics generated by the further reduced dielectric screening effect in the freestanding structure. The formation efficiency of excitonic complexes is enhanced and the multiple biexciton species (five particles such as charged biexcitons and acceptor/donor-bound biexcitons) are successfully induced under low excitation intensity and moderate temperature conditions. Our findings offer valuable insights into the influence of the dielectric environment on exciton interactions and enable a productive avenue for exploring fundamental many-body interactions, providing new possibilities for dielectric engineering of atomic thin semiconductors.
Collapse
Affiliation(s)
- Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
| | - Zhuoyuan Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
- Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, the Australian National University, Canberra, ACT, 2601, Australia.
| |
Collapse
|
2
|
Zhong J, Huang L, Sheng W. Abnormal scaling of excitons in phosphorene quantum dots. Phys Chem Chem Phys 2020; 22:5723-5728. [PMID: 32104811 DOI: 10.1039/c9cp06146k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Excitonic states of a many-electron system in phosphorene quantum dots (PQDs) are investigated theoretically by using a configuration interaction approach. For a triangular PQD in various dielectric environments, its exciton is found to obey two distinct scaling rules. When there is a strong screening effect present in the nanodot, the exciton binding energy (Δex) is shown to be around -150 meV as the long-range Coulomb interactions are totally suppressed and it increases to about 100 meV when the effective dielectric constant (εr) decreases to 12.5. Over this range of εr, Δex is found to be well fitted into a quadratic form of εr-1, which scales neither linearly with εr-2 like the case of bulk three-dimensional semiconductors nor linearly with εr-1 like the case previously reported for graphene nanostructures. When εr is reduced below 10.0, however, Δex is shown to exhibit a perfect linear relationship with εr-1, which behaves just like that of a two-dimensional graphene sheet. On the other hand, with the reduced εr, the quasiparticle gap is found to decrease instead of increasing like in most of the semiconductor nanostructures. As a result, it is revealed that the relationship of Δex with the quasi-particle gap deviates largely from the linear one previously reported for graphene and many other two-dimensional materials.
Collapse
Affiliation(s)
- Jun Zhong
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, P. R. China.
| | - Linan Huang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, P. R. China.
| | - Weidong Sheng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, P. R. China.
| |
Collapse
|
3
|
Abstract
In a conventional semiconductor, when the dielectric screening effect is suppressed, the exciton binding energy increases and the corresponding excitonic transition would exhibit a redshift in the spectrum. In this work, I study the optical properties of hexagonal graphene nanodots by using a configuration interaction approach and reveal that the edge of the absorption spectrum shows an abnormal blueshift as the environmental dielectric constant ϵr decreases. The two dominant many-body effects in the nanodot: the quasiparticle and excitonic effects are both found to scale almost linearly with ϵr-1. The former is shown to have a larger proportionality constant and thus accounts for the blueshift of the absorption edge. In contrast to the long-range Coulomb interaction, the on-site Coulomb energy is found to have a negative impact on the bright excitonic states. In the presence of a strong dielectric screening effect, a strong short-range Coulomb interaction is revealed to be responsible for the disintegration of the bright exciton.
Collapse
Affiliation(s)
- Weidong Sheng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China and Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| |
Collapse
|
4
|
Klots AR, Weintrub B, Prasai D, Kidd D, Varga K, Velizhanin KA, Bolotin KI. Controlled dynamic screening of excitonic complexes in 2D semiconductors. Sci Rep 2018; 8:768. [PMID: 29335642 PMCID: PMC5768700 DOI: 10.1038/s41598-017-18803-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 12/06/2017] [Indexed: 11/18/2022] Open
Abstract
We report a combined theoretical/experimental study of dynamic screening of excitons in media with frequency-dependent dielectric functions. We develop an analytical model showing that interparticle interactions in an exciton are screened in the range of frequencies from zero to the characteristic binding energy depending on the symmetries and transition energies of that exciton. The problem of the dynamic screening is then reduced to simply solving the Schrodinger equation with an effectively frequency-independent potential. Quantitative predictions of the model are experimentally verified using a test system: neutral, charged and defect-bound excitons in two-dimensional monolayer WS2, screened by metallic, liquid, and semiconducting environments. The screening-induced shifts of the excitonic peaks in photoluminescence spectra are in good agreement with our model.
Collapse
Affiliation(s)
- Andrey R Klots
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA
| | - Benjamin Weintrub
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA
- Department of Physics, Freie University, Berlin, 14195, Germany
| | - Dhiraj Prasai
- Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, TN-37234, USA
| | - Daniel Kidd
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA
| | - Kalman Varga
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA
| | - Kirill A Velizhanin
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM-87545, USA
| | - Kirill I Bolotin
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN-37235, USA.
- Department of Physics, Freie University, Berlin, 14195, Germany.
| |
Collapse
|
5
|
Nayak PK, Horbatenko Y, Ahn S, Kim G, Lee JU, Ma KY, Jang AR, Lim H, Kim D, Ryu S, Cheong H, Park N, Shin HS. Probing Evolution of Twist-Angle-Dependent Interlayer Excitons in MoSe 2/WSe 2 van der Waals Heterostructures. ACS NANO 2017; 11:4041-4050. [PMID: 28363013 DOI: 10.1021/acsnano.7b00640] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Interlayer excitons were observed at the heterojunctions in van der Waals heterostructures (vdW HSs). However, it is not known how the excitonic phenomena are affected by the stacking order. Here, we report twist-angle-dependent interlayer excitons in MoSe2/WSe2 vdW HSs based on photoluminescence (PL) and vdW-corrected density functional theory calculations. The PL intensity of the interlayer excitons depends primarily on the twist angle: It is enhanced at coherently stacked angles of 0° and 60° (owing to strong interlayer coupling) but disappears at incoherent intermediate angles. The calculations confirm twist-angle-dependent interlayer coupling: The states at the edges of the valence band exhibit a long tail that stretches over the other layer for coherently stacked angles; however, the states are largely confined in the respective layers for intermediate angles. This interlayer hybridization of the band edge states also correlates with the interlayer separation between MoSe2 and WSe2 layers. Furthermore, the interlayer coupling becomes insignificant, irrespective of twist angles, by the incorporation of a hexagonal boron nitride monolayer between MoSe2 and WSe2.
Collapse
Affiliation(s)
| | - Yevhen Horbatenko
- Center for Multidimensional Carbon Materials (CMCM), Institute of Basic Science (IBS) , Ulsan 44919, Republic of Korea
| | | | | | - Jae-Ung Lee
- Department of Physics, Sogang University , Seoul 04107, Republic of Korea
| | | | | | - Hyunseob Lim
- Department of Chemistry, Chonnam National University , Gwangju 61186, Republic of Korea
| | - Dogyeong Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH) , Pohang, Gyeongbuk 790-784, Republic of Korea
| | - Sunmin Ryu
- Department of Chemistry, Pohang University of Science and Technology (POSTECH) , Pohang, Gyeongbuk 790-784, Republic of Korea
| | - Hyeonsik Cheong
- Department of Physics, Sogang University , Seoul 04107, Republic of Korea
| | - Noejung Park
- Center for Multidimensional Carbon Materials (CMCM), Institute of Basic Science (IBS) , Ulsan 44919, Republic of Korea
| | - Hyeon Suk Shin
- Center for Multidimensional Carbon Materials (CMCM), Institute of Basic Science (IBS) , Ulsan 44919, Republic of Korea
| |
Collapse
|
6
|
Wang H, Sheng W. Excitonic absorption spectra in graphene nanoflakes: Tuning of exciton binding energy by dielectric environments. J Chem Phys 2017; 146:084705. [PMID: 28249450 DOI: 10.1063/1.4977199] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
By solving the Bethe-Salpeter equation within the Hartree-Fock formalism, we study the excitonic absorption spectra of graphene nanoflakes embedded in various dielectric environments. With the excitonic effects fully taken into account, the exciton binding energy as a function of the dielectric constant is found to be well described by a single scaling rule in which the scaling factor is found to vary slowly with the size of the nanoflakes. Furthermore, it is revealed that the exciton binding energy scales almost linearly with the on-site interaction energy and exhibits more sensitive dependence in smaller nanoflakes. Our results are found to agree well with the recent experiment.
Collapse
Affiliation(s)
- Hao Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China
| | - Weidong Sheng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China and Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| |
Collapse
|
7
|
Zhang Y, Sheng W, Li Y. Dark excitons and tunable optical gap in graphene nanodots. Phys Chem Chem Phys 2017; 19:23131-23137. [DOI: 10.1039/c7cp04591c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
By using a configuration interaction approach with up to the fifth excitations taken into account, we study the excitonic effect in the optical absorption in graphene nanodots.
Collapse
Affiliation(s)
- Yingjie Zhang
- State Key Laboratory of Surface Physics and Department of Physics
- Fudan University
- Shanghai 200433
- China
| | - Weidong Sheng
- State Key Laboratory of Surface Physics and Department of Physics
- Fudan University
- Shanghai 200433
- China
- Collaborative Innovation Center of Advanced Microstructures
| | - Yang Li
- State Key Laboratory of Surface Physics and Department of Physics
- Fudan University
- Shanghai 200433
- China
| |
Collapse
|
8
|
Abstract
The binding energy of an exciton in a semiconductor or an insulator is known to scale linearly with εr-2, where εr is its dielectric constant. In graphene however, since the kinetic energy scales linearly with the wave number instead of its square, the exciton binding energy is thus expected to scale with εr-1. In this work we make use of the configuration interaction approach to study the properties of excitons in graphene nanodots embedded in various dielectric environments. With tens of million configurations taken into account in the calculation, we find that the exciton binding energy can be well described by a single scaling rule in which the scaling factor is found to vary with the dimension of the nanodots as well as with the on-site interaction parameter, which agrees well with a recent experiment. The linear relation of the exciton binding energy found with the quasi-particle gap also agrees with the previous work on bulk graphene and other two-dimensional materials.
Collapse
Affiliation(s)
- Weidong Sheng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China. and Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China
| | - Hao Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
| |
Collapse
|
9
|
Barisien T, Legrand L, Mu Z, Hameau S. Excitonic linewidth of organic quantum wires generated in reduced dimensionality matrices. Phys Chem Chem Phys 2016; 18:12928-37. [DOI: 10.1039/c6cp00629a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nanostructured crystalline film achieving a 2D bath for single conjugated polymer chain linewidth spectroscopy.
Collapse
Affiliation(s)
- Thierry Barisien
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| | - Laurent Legrand
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| | - Zhao Mu
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| | - Sophie Hameau
- Sorbonne Universités
- UPMC Université Paris 06
- CNRS-UMR 7588
- Institut des NanoSciences de Paris
- Paris
| |
Collapse
|