Wannier interpolation of spin accumulation coefficient
ORAL
Abstract
Spin Hall (SH) effect is a phenomenon in which spin current flows perpendicular to an electric field and turns into the spin accumulation at the surface. Such spin generation can be realized even in nonmagnetic systems owing to spin-orbit coupling (SOC). The SH conductivity, namely, the response of spin current to the electric field, has been widely evaluated as an indicator of the SH effect. However, spin current is ambiguous in the presence of SOC, and the SH conductivity depends on the definition of spin current.
In contrast, spin is unique, and the spin accumulation has been experimentally observed [1]. The spatial distribution of spin for the disordered Rashba model has been numerically studied by solving the diffusion equation [2] and the Landauer-Keldysh formalism [3]. However, it is difficult to apply these methods to real materials because we need to impose the open boundary conditions and deal with disorder. Recently, it was suggested that the spin accumulation coefficient (SAC), namely, the response of spin to the electric field gradient, characterizes the spin accumulation owing to the SH effect [4]. Counterintuitively, the SAC can be evaluated as a bulk property using Bloch wavefunctions and is an alternative indicator of the SH effect.
Here we develop an ab initio computational scheme for the SAC [5]. With the help of maximally localized Wannier functions implemented in Wannier90 [6], we can evaluate the SAC with high precision for real materials. We apply our method to monolayer transition metal dichalcogenide MoS2 and trigonal tellurium to confirm the consistency with the point group symmetry and the gauge invariance regarding Wannier functions. Our work paves the way to quantitative materials research on the SH effect without any ambiguity.
[1] Y. K. Kato et al., Science 306, 1910 (2004).
[2] E. I. Rashba, Physica E 34, 31 (2006).
[3] B. K. Nikolic et al., Phys. Rev. Lett. 95, 046601 (2005).
[4] A. Shitade and G. Tatara, Phys. Rev. B 105, L201202 (2022).
[5] A. Shitade and E. Minamitani, npj Spintron. 3, 29 (2025).
[6] G. Pizzi et al., J. Phys.: Condens. Matter 32, 165902 (2020).
In contrast, spin is unique, and the spin accumulation has been experimentally observed [1]. The spatial distribution of spin for the disordered Rashba model has been numerically studied by solving the diffusion equation [2] and the Landauer-Keldysh formalism [3]. However, it is difficult to apply these methods to real materials because we need to impose the open boundary conditions and deal with disorder. Recently, it was suggested that the spin accumulation coefficient (SAC), namely, the response of spin to the electric field gradient, characterizes the spin accumulation owing to the SH effect [4]. Counterintuitively, the SAC can be evaluated as a bulk property using Bloch wavefunctions and is an alternative indicator of the SH effect.
Here we develop an ab initio computational scheme for the SAC [5]. With the help of maximally localized Wannier functions implemented in Wannier90 [6], we can evaluate the SAC with high precision for real materials. We apply our method to monolayer transition metal dichalcogenide MoS2 and trigonal tellurium to confirm the consistency with the point group symmetry and the gauge invariance regarding Wannier functions. Our work paves the way to quantitative materials research on the SH effect without any ambiguity.
[1] Y. K. Kato et al., Science 306, 1910 (2004).
[2] E. I. Rashba, Physica E 34, 31 (2006).
[3] B. K. Nikolic et al., Phys. Rev. Lett. 95, 046601 (2005).
[4] A. Shitade and G. Tatara, Phys. Rev. B 105, L201202 (2022).
[5] A. Shitade and E. Minamitani, npj Spintron. 3, 29 (2025).
[6] G. Pizzi et al., J. Phys.: Condens. Matter 32, 165902 (2020).
*This work was supported by the Japan Society for the Promotion of Science KAKENHI (Grants No. JP22K03498 and No. JP23K21081).
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Presenters
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Atsuo Shitade
- Institute of Scientific and Industrial Research, The University of Osaka