The Shift of the Branch Point in the Mass Operator of Formal Perturbation Theory for a Nonideal Fermi-Dirac System

В. В. Толмачев

В. В. Толмачев

В. В. Толмачев

Robert William Jones, Franz Mohling, Richard L. Becker

Victor M. Galitski, VICTOR A. KHODEL

We study the renormalization of the Fermi-liquid parameters in the vicinity of a density wave quantum phase transition, which should occur in MOSFET systems at low densities. First, using a perturbative RPA treatment of fluctuations, we calculate the electronic self-energy and show that the effective mass diverges at the density wave transition point. Second, we go beyond perturbation theory, making use of the exact Pitaevskii identities. Within this exact analysis, we also find a divergence of the effective mass, which occurs at higher densities in the fluctuation region, as compared to the perturbation theory. This result signals the break-down of conventional Fermi-liquid description in the vicinity of the transition point. The divergence of the effective mass gives rise to a singular behavior of the electronic compressibility. We suggest that the experimentally observed enhancement of the effective mass is a precursor to a second order thermodynamic phase transition into a glassy density wave state.

А. А. Повзнер, Yu. A. Kukharenko

This paper is a study in a possible steady-state perturbation theory for arbitrary excited multiply degenerate states of a normal Fermi system in the statistical limit. An operator technique has been developed to transform the relevant Hamiltonian into an operator that is a function of occupation number operators only. The perturbation theory equations have been proved to be solvable in the space of quasinormal form operators and their formal solutions have been derived. It is shown that the operator series of perturbation theory can be transformed to a linked cluster expansion with the nonphysical powers of volume eliminated. Elimination of nonphysical terms is effected without use of the diagrams technique.