Motion of 2D exciton in momentum space leads to pseudospin distribution narrowing on the Bloch Sphere
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| Main Authors: | , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866910439939506176 |
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| author | Gupta, Garima Watanabe, Kenji Taniguchi, Takashi Majumdar, Kausik |
| author_facet | Gupta, Garima Watanabe, Kenji Taniguchi, Takashi Majumdar, Kausik |
| contents | Motional narrowing implies narrowing induced by motion, for example, in nuclear resonance, the thermally induced random motion of the nuclei in an inhomogeneous environment leads to counter-intuitive narrowing of the resonance line. Similarly, the excitons in monolayer semiconductors experience magnetic inhomogeneity: the electron-hole spin-exchange interaction manifests as an in-plane pseudo-magnetic field with a periodically varying orientation inside the exciton band. The excitons undergo random momentum scattering and pseudospin precession repeatedly in this inhomogeneous magnetic environment - typically resulting in fast exciton depolarization. On the contrary, we show that such magnetic inhomogeneity averages out at high scattering rate due to motional narrowing. Physically, a faster exciton scattering leads to a narrower pseudospin distribution on the Bloch sphere, implying a nontrivial improvement in exciton polarization. The in-plane nature of the pseudo-magnetic field enforces a contrasting scattering dependence between the circularly and linearly polarized excitons - providing a spectroscopic way to gauge the sample quality. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2404_15120 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Motion of 2D exciton in momentum space leads to pseudospin distribution narrowing on the Bloch Sphere Gupta, Garima Watanabe, Kenji Taniguchi, Takashi Majumdar, Kausik Mesoscale and Nanoscale Physics Materials Science Applied Physics Optics Motional narrowing implies narrowing induced by motion, for example, in nuclear resonance, the thermally induced random motion of the nuclei in an inhomogeneous environment leads to counter-intuitive narrowing of the resonance line. Similarly, the excitons in monolayer semiconductors experience magnetic inhomogeneity: the electron-hole spin-exchange interaction manifests as an in-plane pseudo-magnetic field with a periodically varying orientation inside the exciton band. The excitons undergo random momentum scattering and pseudospin precession repeatedly in this inhomogeneous magnetic environment - typically resulting in fast exciton depolarization. On the contrary, we show that such magnetic inhomogeneity averages out at high scattering rate due to motional narrowing. Physically, a faster exciton scattering leads to a narrower pseudospin distribution on the Bloch sphere, implying a nontrivial improvement in exciton polarization. The in-plane nature of the pseudo-magnetic field enforces a contrasting scattering dependence between the circularly and linearly polarized excitons - providing a spectroscopic way to gauge the sample quality. |
| title | Motion of 2D exciton in momentum space leads to pseudospin distribution narrowing on the Bloch Sphere |
| topic | Mesoscale and Nanoscale Physics Materials Science Applied Physics Optics |
| url | https://arxiv.org/abs/2404.15120 |