Thermodynamic Compressibility Measurements in the Context of 2D Metal–Insulator Transition

Abstract

Presented in this work is a comparative study of the thermodynamic compressibility of two different two dimensional systems in GaAs/AlGaAs heterostructures. In the two-dimensional hole system, electron–electron interactions are strong and possibly the reason for an anomalous temperature dependence in the resistivity that is reminiscent of metallic behavior which is known not to exist in a non-interacting two dimensional Fermi gas. The other system is a two-dimensional electron system where interactions are much weaker and whose transport properties have been understood in the context of scaling theory. The thermodynamic compressibility of both systems are measured. An unequivocal signature for a phase transition is found in the compressibility measurements for the hole system. In contrast, a very different, non-singular behavior is observed in the electron system. The experimental results are compared with a recent theoretical work.