Non-Hermitian theory of valley excitons in two-dimensional semiconductors
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arXiv
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| Autori principali: | , , |
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| Natura: | Preprint |
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2024
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| _version_ | 1866929620869185536 |
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| author | Wang, Qiutong Li, Ci Tong, Qingjun |
| author_facet | Wang, Qiutong Li, Ci Tong, Qingjun |
| contents | Electron-hole exchange interaction in two-dimensional transition metal dichalcogenides is extremely strong due to the dimension reduction, which promises valley-superposed excitonic states with linearly polarized optical emissions. However, strong circular polarization reflecting valley-polarized excitonic states is commonly observed in helicity-resolved optical experiments. Here we present a non-Hermitian theory of valley excitons by incorporating optical pumping and intrinsic decay, which unveils an anomalous valley-polarized excitonic state with elliptically polarized optical emission. This novel state arises from the non-Hermiticity induced parity-time ($\mathcal{PT}$)-symmetry breaking, which impedes the experimental observation of intervalley excitonic coherence effect. At large excitonic center-of-mass momenta, the $\mathcal{PT}$-symmetry is restored and the excitonic states recover their valley coherence. Interestingly, the linear polarization directions in optical emissions from these valley-superposed excitonic states are non-orthogonal and even become parallel at exceptional points. Our non-Hermitian theory also predicts a non-zero Berry curvature for valley excitons, which admits a topological excitonic Hall transport beyond the Hermitian predictions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2405_19007 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Non-Hermitian theory of valley excitons in two-dimensional semiconductors Wang, Qiutong Li, Ci Tong, Qingjun Mesoscale and Nanoscale Physics Electron-hole exchange interaction in two-dimensional transition metal dichalcogenides is extremely strong due to the dimension reduction, which promises valley-superposed excitonic states with linearly polarized optical emissions. However, strong circular polarization reflecting valley-polarized excitonic states is commonly observed in helicity-resolved optical experiments. Here we present a non-Hermitian theory of valley excitons by incorporating optical pumping and intrinsic decay, which unveils an anomalous valley-polarized excitonic state with elliptically polarized optical emission. This novel state arises from the non-Hermiticity induced parity-time ($\mathcal{PT}$)-symmetry breaking, which impedes the experimental observation of intervalley excitonic coherence effect. At large excitonic center-of-mass momenta, the $\mathcal{PT}$-symmetry is restored and the excitonic states recover their valley coherence. Interestingly, the linear polarization directions in optical emissions from these valley-superposed excitonic states are non-orthogonal and even become parallel at exceptional points. Our non-Hermitian theory also predicts a non-zero Berry curvature for valley excitons, which admits a topological excitonic Hall transport beyond the Hermitian predictions. |
| title | Non-Hermitian theory of valley excitons in two-dimensional semiconductors |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2405.19007 |