The low-temperature collapse of the Fermi surface and phase transitions in correlated Fermi systems

TL;DR

This paper investigates how the Fermi surface collapses at low temperatures in strongly correlated Fermi systems, leading to a topological crossover, altered phase transition behavior, and implications for superconductivity.

Contribution

It demonstrates the collapse of the Fermi surface causes a narrowing of the Fermi liquid regime and results in a split of the BCS superconducting transition.

Findings

Fermi liquid regime dramatically narrows at low temperatures.

Collapse of the Fermi surface affects pairing correlations.

Superconducting transition splits into two separate transitions.

Abstract

A topological crossover, associated with the collapse of the Fermi surface in strongly correlated Fermi systems, is examined. It is demonstrated that in these systems, the temperature domain where standard Fermi liquid results hold dramatically narrows, because the Landau regime is replaced by a classical one. The impact of the collapse of the Fermi surface on pairing correlations is analyzed. In the domain of the Lifshitz phase diagram where the Fermi surface collapses, splitting of the BCS superconducting phase transition into two different ones of the same symmetry is shown to occur.