Valley-dependent many-body effects in two-dimensional semiconductors

We calculate the valley degeneracy (g(v)) dependence of the many-body renormalization of quasiparticle properties in multivalley two-dimensional (2D) semiconductor structures due to the Coulomb interaction between the carriers. Quite unexpectedly, the g(v) dependence of many-body effects is nontrivial and nongeneric, and depends qualitatively on the specific Fermi-liquid property under consideration. While the interacting 2D compressibility manifests monotonically increasing many-body renormalization with increasing g(v), the 2D spin susceptibility exhibits an interesting nonmonotonic g(v) dependence with the susceptibility increasing (decreasing) with g(v) for smaller (larger) values of g(v) with the renormalization effect peaking around g(v) similar to 1-2. Our theoretical results provide a clear conceptual understanding of recent valley-dependent 2D susceptibility measurements in AlAs quantum wells.