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

摘要

Low-field magnetotransport measurements on a high-mobility (μ= 110,000 cm~2/Vs) two-dimensional 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 ρ_(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.