Even Integer Quantum Hall Effect in Materials with Hidden Spin Texture

TL;DR

This paper demonstrates that hidden Rashba spin-orbit coupling in centrosymmetric 2D materials can produce an even-integer quantum Hall effect, revealing the impact of hidden spin textures on topological electronic properties.

Contribution

It introduces a theoretical framework showing how hidden SOC in centrosymmetric materials leads to even-integer quantum Hall plateaus, a novel insight into spin textures and topological phases.

Findings

Hidden Rashba SOC causes even-integer quantum Hall plateaus.

Hybridization of degenerate Rashba layers suppresses spin splitting.

Breaking inversion symmetry restores conventional quantum Hall effects.

Abstract

Because spin-orbit coupling (SOC) is invisible in the band structure when inversion symmetry exists, whether spins are trivially degenerate or strongly coupled to momentum due to SOC is presumed to make little difference in transport measurements, such as magnetoresistance and quantum oscillations. In this work, however, we show that hidden Rashba SOC in a centrosymmetric two-dimensional material can lead to the quantum Hall effect with only even-integer plateaus, unlike a spinless electron gas. Here, two Rashba layers that are degenerate but with opposite SOC due to inversion symmetry, hybridize with each other and create two doubly-degenerate bands with hidden spin texture. Correspondingly, two branches of Landau levels interact, resulting in significant suppression of spin splitting due to the balancing of intralayer SOC and interlayer hybridization. Furthermore, we show that breaking inversion symmetry restores the ordinary quantum Hall fluid by introducing spin-split Fermi surfaces. Our theory can apply to centrosymmetric materials with strong SOC, as demonstrated in a recent experiment on the two-dimensional semiconductor Bi$_2$O$_2$Se.