Valley splitting of Si/SiGe heterostructures in tilted magnetic fields

Abstract

We have investigated the valley splitting of two-dimensional electrons in high quality Si/Si${}_{1-x}$Ge${}_x$ heterostructures under tilted magnetic fields. For all the samples in our study, the valley splitting at filling factor $\hat{I}½=3$ ($\hat{I}{”}_3$) is significantly different before and after the coincidence angle, at which energy levels cross at the Fermi level. On both sides of the coincidence, a linear density dependence of $\hat{I}{”}_3$ on the electron density was observed, while the slope of these two configurations differs by more than a factor of two. We argue that screening of the Coulomb interaction from the low-lying filled levels, which also explains the observed spin-dependent resistivity, is responsible for the large difference of $\hat{I}{”}_3$ before and after the coincidence.

REVTEX 4 pages, 4 figures