Valley- and spin-dependent quantum Hall states in bilayer silicene

TL;DR

This paper investigates the quantum Hall effect in bilayer silicene, revealing unique valley- and spin-dependent quantization patterns influenced by external fields and intrinsic material properties.

Contribution

It demonstrates the distinct quantum Hall step structure in bilayer silicene, highlighting effects of valley, spin-orbit coupling, and external electric fields on conductivity quantization.

Findings

Quantized Hall conductivity differs from graphene due to valley and spin effects.

Conductivity plateaux have different step values for conduction and valence bands.

External electric fields induce fractional quantum Hall states by Landau level mixing.

Abstract

The Hall conductivity $\sigma_{xy}$ of many condensed matter systems presents a step structure when a uniform perpendicular magnetic field is applied. We report the quantum Hall effect in buckled AB-bottom-top bilayer silicene and its robust dependence on the electronic valley and spin-orbit coupling. With the unique multi-valley electronic structure and the lack of spin degeneracy, the quantization of the Hall conductivity in this system is unlike the conventional sequence as reported for graphene. Furthermore, the conductivity plateaux take different step values for conduction ($2e^2/h$) and valence ($6e^2/h$) bands since their originating valleys present inequivalent degeneracy. We also report the emergence of fractions under significant effect of a uniform external electric field on the quantum Hall step structure by the separation of orbital distributions and the mixing of Landau levels from distinct valleys. The valley- and spin-dependent quantum Hall conductivity arises from the interplay of lattice geometry, atomic interaction, spin-orbit coupling, and external magnetic and electric fields.