Valley Polarization in Si(100) at Zero Magnetic Field

TL;DR

This paper demonstrates that valley splitting and valley polarization in Si(100) quantum wells occur at zero magnetic field and are observable through conductance steps, persisting at high temperatures without magnetic field dependence.

Contribution

It provides direct transport evidence of valley splitting and polarization in Si(100) at zero magnetic field, a novel observation in silicon quantum wells.

Findings

Valley splitting manifests as a conductance step.

Valley polarization exists at zero magnetic field.

The phenomenon persists at high temperatures.

Abstract

The valley splitting, which lifts the degeneracy of the lowest two valley states in a SiO$_2$/(100)Si/SiO$_2$ quantum well is examined through transport measurements. We demonstrate that the valley splitting can be observed directly as a step in the conductance defining a boundary between valley-unpolarized and polarized regions. This persists to well above liquid helium temperature and shows no dependence on magnetic field, indicating that single-particle valley splitting and valley-polarization exist in (100) silicon even at zero magnetic field.