Integer quantum Hall effect on a six valley hydrogen-passivated silicon (111) surface

TL;DR

This study investigates the integer quantum Hall effect in a two-dimensional electron system on hydrogen-passivated Si(111) surfaces, revealing valley degeneracy breaking and anisotropic resistance, with implications for understanding electron interactions.

Contribution

It provides experimental evidence of valley degeneracy breaking and anisotropy in Si(111) surfaces, highlighting effects beyond non-interacting electron models.

Findings

Sixfold valley degeneracy is broken in the system.

Unequal occupation of valleys leads to resistance anisotropy.

Observation of odd filling factors suggests electron interactions are significant.

Abstract

We report magneto-transport studies of a two-dimensional electron system formed in an inversion layer at the interface between a hydrogen-passivated Si(111) surface and vacuum. Measurements in the integer quantum Hall regime demonstrate the expected sixfold valley degeneracy for these surfaces is broken, resulting in an unequal occupation of the six valleys and anisotropy in the resistance. We hypothesize the misorientation of Si surface breaks the valley states into three unequally spaced pairs, but the observation of odd filling factors, is difficult to reconcile with non-interacting electron theory.