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Ultrafast control of the valley and spin polarization in Transition-metal dichalcogenides
https://repo.qst.go.jp/records/85756
https://repo.qst.go.jp/records/85756a590a611-0c0f-4891-b3ce-9a46dd7cf8d6
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2022-02-04 | |||||
| タイトル | ||||||
| タイトル | Ultrafast control of the valley and spin polarization in Transition-metal dichalcogenides | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||
| 資源タイプ | conference object | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
Hashmi, Arqum
× Hashmi, Arqum× Yamada, Shunsuke× Yamada, Atsushi× Kazuhiro, Yabana× Tomohito, Otobe× Hashmi, Arqum× Kazuhiro, Yabana× Tomohito, Otobe |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Very short valley lifetimes (~10^3-10^6 femtoseconds (fs)) demands the ultrafast control of valley selection on fs time scale. In this work, we explore the possibility to induce valley asymmetry by single-cycle linearly polarized laser pulse in WSe2 monolayer. By combining the time-dependent density functional theory with the two-band massive Dirac Hamiltonian, we study the various factors that are vital for valley polarization by linearly polarized laser pulse both in linear and non-linear optics limits. In contrast to long pulses, ultrashort pulses containing few optical cycles, the condition (maxima of E(t)=0 of A(t)) can be controlled by CEP (φ). φ is the relative phase of the pulse envelope and the oscillating electric field which plays a significant role in the pulse waveform for ultrashort laser pulses. To explore the φ dependence on valley pseudospin, we apply linearly polarized pulses parallel to armchair (Γ-M) and zigzag (Γ-K) directions. Valley polarization does not exist for the field polarized along Γ-M because of the lattice symmetry in that direction. On the other hand, owing to trigonal wrapping, the polarization parallel to Γ-K experiences different band curvature with respect to K and K' point. The valley polarization for weak intensity is zero for all φ confirm the fact that the valley polarization is absent within the linear-optical limit. By increasing the intensity, we enter in the nonlinear regime and the substantial valley polarization is observed. The valley polarization increases gradually with φ and reaches its maximum value at φ = π/2, shows a typical sine wave curve. Valley polarization is robust against field strength but in all cases oscillate as a function of CEP. The spin polarization (N _↑ - N _↓) is negligible and independent of intensity and φ. Degree of spin polarization (N _↑- N _↓) / (N _↑+ N _↓) follow the same behavior as valley polarization which shows that spin polarization is also an observable along with valley polarization. |
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| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 69th JSAP Spring Meeting 2022 | |||||
| 発表年月日 | ||||||
| 日付 | 2022-03-25 | |||||
| 日付タイプ | Issued | |||||
