Temperature-dependent transport in a sixfold degenerate two-dimensional electron system on a H-Si(111) surface

TL;DR

This study investigates the temperature-dependent electrical transport properties of a high-mobility two-dimensional electron system on H-Si(111), revealing sixfold valley degeneracy, a small valley splitting, and insights into valley drag and Fermi liquid behavior.

Contribution

It introduces a method to probe intervalley momentum transfer using the low-field Hall coefficient in a 2D electron system with high valley degeneracy.

Findings

Strong temperature dependence of resistivity observed between 0.07 and 25 K.

Valley degeneracy confirmed to be sixfold with splitting <= 0.1 K.

Relaxation rate aligns with Fermi liquid theory, residual drag remains unexplained.

Abstract

Low-field magnetotransport measurements on a high mobility (mu=110,000 cm^2/Vs) two-dimensional (2D) electron system on a H-terminated Si(111) surface reveal a sixfold valley degeneracy with a valley splitting <= 0.1 K. The zero-field resistivity rho_{xx} displays strong temperature dependence for 0.07 < T < 25 K as predicted for a system with high degeneracy and large mass. We present a method for using the low-field Hall coefficient to probe intervalley momentum transfer (valley drag). The relaxation rate is consistent with Fermi liquid theory, but a small residual drag as T->0 remains unexplained.