Electric field effect on electron spin splitting in SiGe/Si quantum wells

TL;DR

This paper investigates how electric fields influence electron spin splitting in SiGe/Si quantum wells using microscopic tight-binding calculations, revealing oscillatory behavior and the effects of asymmetry and electric fields.

Contribution

It provides a detailed theoretical analysis of electric field effects on spin splitting in SiGe/Si quantum wells, incorporating tight-binding and envelope function approaches.

Findings

Spin splitting oscillates with quantum well width due to valley reflection.

Electric fields suppress oscillations in spin splitting.

Additional electric-field-induced terms appear in the spin Hamiltonian.

Abstract

Effect of electric field on spin splitting in SiGe quantum wells (QWs) has been studied theoretically. Microscopical calculations of valley and spin splittings are performed in the effective $sp^3d^5s^*$ tight-binding model. The splittings oscillate as a function of the QW width due to inter-valley reflection of the electron wave off the interfaces. In accordance with the symmetry considerations additional electric-field-induced terms appear in the electron spin-dependent Hamiltonian. The oscillations of splitting are suppressed in rather low electric fields. The tight-binding calculations have been analyzed by using the envelope function approach extended to asymmetrical QWs.