Effects of interactions and disorder on the compressibility of two-dimensional electron and hole systems

摘要

We have studied the thermodynamic compressibility of 2D electron and 2D hole gases near the apparent metal-insulator transition, in the ranges of the interaction parameter r_s=1-2.5 and r_s=10-30, respectively. Nonmonotonic dependence of the inverse compressibility on the carrier density is observed with an upturn at low densities. Despite the large difference in r_s, this behaviour of inverse compressibility in both electron and hole systems can be quantitatively accounted for by a nonlinear screening of disorder by the carriers, in particular, by the disorder-driven proliferation of depletion regions in the 2D channel.