Quantum Hall effect in a two-dimensional semiconductor with large spin-orbit coupling

Abstract

We perform magnetotransport studies of atomically thin InSe field-effect transistors with large Rashba spin-orbit coupling (SOC), and extract the Landau level (LL) gaps via thermal activation measurements. Surprisingly, the Landau level gaps at even and odd filling factors are extrapolated to have positive and negative intercepts at $B=0$, respectively, which result from the spin-split Landau spectrum. We also show that for a material with large spin-orbit coupling, its LL gaps may vary nonlinearly and nonmonotonically as a function of magnetic field. Thus, its effective mass and $g$-factor cannot be reliably extracted using conventional expressions, but depend rather sensitively on the SOC's strength and tunability.