Quantum states and linear response in dc and electromagnetic fields for charge current and spin polarization of electrons at Bi/Si interface with giant spin-orbit coupling

TL;DR

This paper extends a nearly free-electron model to analyze quantum states, band structure, and spin polarization at the Bi/Si interface with giant spin-orbit coupling, revealing anisotropic responses to external fields.

Contribution

It develops a detailed model for the Bi/Si interface, enabling analysis of spin-dependent properties and linear response to electromagnetic fields at room temperature.

Findings

Large spin-orbit coupling allows spin resolution at room temperature.

External field orientation influences spin and current anisotropically.

Electromagnetic waves can excite out-of-plane spin components.

Abstract

An expansion of the nearly free-electron model constructed by Frantzeskakis, Pons and Grioni [Phys. Rev. B {\bf 82}, 085440 (2010)] describing quantum states at Bi/Si(111) interface with giant spin-orbit coupling is developed and applied for the band structure and spin polarization calculation, as well as for the linear response analysis for charge current and induced spin caused by dc field and by electromagnetic radiation. It is found that the large spin-orbit coupling in this system may allow resolving the spin-dependent properties even at room temperature and at realistic collision rate. The geometry of the atomic lattice combined with spin-orbit coupling leads to an anisotropic response both for current and spin components related to the orientation of the external field. The in-plane dc electric field produces only the in-plane components of spin in the sample while both the in-plane and out-of-plane spin components can be excited by normally propagating electromagnetic wave with different polarizations.