二次元WTe₂の非線形光学特性に関する計算

概要

令和 4 年度

京都大学化学研究所 スーパーコンピュータシステム 利用報告書
二次元 WTe2 の非線形光学特性に関する計算

Simulation studies of nonlinear optical properties in two-dimensional Wely semimetal WTe2
Optical Nano-science group, Institute of Advanced Energy, Kyoto University
Yubei Xiang
研究成果概要
The Wely semimetal tungsten ditelluride (WTe2) has attracted immense interest due to its
fascinating physical properties and important applications as an example of topological quantum
materials [1]. The novel phenomena of giant magneto-resistance are observed in Wely
semimetal WTe2 [2]. The electronic band structures of thin layered WTe2 are determined by its
layer number and stacking configuration including crystalline symmetry [3,4], which further
influence the linear and nonlinear optical responses. In this study, we have simulated the linear
and nonlinear optical responses of a few layer WTe2 based on a real-time first principles
approach including quasiparticle corrections. The electronic and optical properties in various
structures of WTe2 with different phases and stacking configurations were simulated by
Quantum Espresso [5] and Yambo code [6]. The linear optical responses were calculated by
Bethe-Salpeter equation (BSE)-GW methods and the nonlinear optical responses of second
harmonic generation (SHG) were simulated by independent particle approximation (IPA) with
quasi-particle corrections.
The monolayer 1T’- WTe2 with P21/m space group shows inactivity of SHG signals, while the
monolayer Td- WTe2 with Pm space group shows strong activity of SHG signals. The strong
anisotropic second-order nonlinear susceptibility is observed due to low-symmetry crystal
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structures in monolayer Td- WTe2. Moreover, the monolayer 2H- WTe2 with P6m2 space group
shows activity of SHG signals, as similar to the other semiconducting MX2 (M=Mo, W, X=S,
Se). The results show that WTe2 has unique phase-dependent optical properties including
nonlinear optical responses, which are different from other two-dimensional transition metal
dichalcogenides.
[1] S. Kimura, et al. Phys. Rev. B 99, 195203 (2019).
[2] Y. Wang, et al. Nano Lett. 19, 3969–3975 (2019).
[3] E. J. Sie, et al. Nature 565, 61 (2019).
[4] J. Xiao et al. Nat. Phys. 16, 1028 (2020).
[5] P. Giannozzi et al., J. Phys.: Cond. Mat. 29, 465901 (2017).
[6] D. Sangalli et al., J. Phys.: Cond. Mat. 31, 325902 (2019). ...