On the Theory of the Pseudogap Formation in 2D Attracting Fermion Systems

TL;DR

This paper develops a theoretical model for a new pseudogap phase in 2D fermion systems with phonon-mediated attraction, showing its existence at low carrier densities and discussing implications for high-temperature superconductors.

Contribution

It introduces a novel nonsuperconducting pseudogap phase arising from attraction in 2D fermion systems, expanding understanding of phase behavior in such materials.

Findings

The pseudogap phase exists at low carrier density.

The phase's existence diminishes with increased doping.

The model relates to high-temperature superconductor behavior.

Abstract

Two-dimensional system of the fermions with the indirect Einstein phonon-exchange attraction and added local four-fermion interaction is considered. It is shown that in such a system at resulting attraction between particles a new nonsuperconducting phase arises along with the normal and superconducting phases. In this, called "abnormal normal", or pseudogap, phase the absolute value of the order parameter is finite but its phase is a random quantity. It is important that the new phase really exists at low carrier density only, i.e. it shrinks with doping increasing in the case of phonon attraction. The relevance of the results for high-temperature superconductors is speculated. Key words: 2D metal, arbitrary carrier density, normal phase, abnormal normal phase, pseudogap, suderconducting phase, Berezinskii-Kosterlitz-Thouless phase, electron-electron and electron-hole pairing