Thermodynamic properties of Fermi systems with flat single-particle spectra

TL;DR

This paper explores the thermodynamic behavior of strongly correlated Fermi systems with flat spectra, revealing modifications to Landau theory and analyzing quantum phase transitions beyond traditional models.

Contribution

It demonstrates the applicability of Landau-Migdal quasiparticle theory in flat-spectrum regimes and examines stability and phase transition characteristics.

Findings

Landau-Migdal quasiparticle picture remains valid

Low-temperature properties significantly differ from standard Landau theory

Stability conditions and quantum phase transition nature are clarified

Abstract

The behavior of strongly correlated Fermi systems is investigated beyond the onset of a phase transition where the single-particle spectrum $\xi({\bf p})$ becomes flat. The Landau-Migdal quasiparticle picture is shown to remain applicable on the ordered side of this transition. Nevertheless, low-temperature properties evaluated within this picture show profound changes relative to results of Landau theory, as a direct consequence of the flattening of $\xi({\bf p})$. Stability conditions for this class of systems are examined, and the nature of antiferromagnetic quantum phase transitions is elucidated.