The Electrical and Spin Properties of Monolayer and Bilayer Janus HfSSe under Vertical Electrical Field

TL;DR

This study investigates how vertical electric fields influence the electrical and spin properties of monolayer and bilayer Janus HfSSe, revealing controllable bandgap tuning and spin splitting effects relevant for electronic and spintronic applications.

Contribution

It provides a comprehensive analysis of the electric field effects on various stacking orders of bilayer HfSSe, highlighting tunable bandgap and spin splitting phenomena.

Findings

Electric field can close the bilayer bandgap, inducing a semiconductor-metal transition.

Spin-orbit coupling causes notable band splitting, enhanced by electric fields.

Stacking configurations without mirror symmetry exhibit and enhance Rashba spin splitting.

Abstract

In this paper, the electrical and spin properties of mono- and bilayer HfSSe in the presence of a vertical electric field are studied. The density functional theory is used to investigate their properties. Fifteen different stacking orders of bilayer HfSSe are considered. The mono- and bilayer demonstrate an indirect bandgap, whereas the bandgap of bilayer can be effectively controlled by electric field. While the bandgap of bilayer closes at large electric fields and a semiconductor to metal transition occurs, the effect of a normal electric field on the bandgap of the monolayer HfSSe is quite weak. Spin-orbit coupling causes band splitting in the valence band and Rashba spin splitting in the conduction band of both mono- and bilayer structures. The band splitting in the valence band of the bilayer is smaller than a monolayer, however, the vertical electric field increases the band splitting in bilayer one. The stacking configurations without mirror symmetry exhibit Rashba spin splitting which is enhanced with the electric field.