Breakdown of Landau Fermi liquid properties in the $2D$ Boson-Fermion model

TL;DR

This paper investigates the breakdown of Landau Fermi liquid behavior in a 2D Boson-Fermion model, revealing how fermionic excitations deviate from conventional properties near the Fermi surface.

Contribution

It provides a detailed analysis of the spectral properties and quasiparticle behavior in the Boson-Fermion model, highlighting deviations from standard Fermi liquid theory.

Findings

Fermionic dispersion flattens near the Fermi vector, indicating precursor signs of superconductivity.

Quasiparticle widths increase as temperature decreases, contrary to typical Fermi liquids.

The fermionic distribution function shows strong temperature-dependent modifications below the Fermi surface.

Abstract

We study the normal state spectral properties of the fermionic excitations in the Boson-Fermion model. The fermionic single particle excitations show a flattening of the dispersion as the Fermi vector ${\bf k}_{_F}$ is approached from below, forshadowing a Bogoliubov spectrum of a superconducting ground state. The width of the quasiparticle excitations near ${\bf k}_{_F}$ increases monotonically as the temperature is lowered. In the fermionic distribution function this temperature dependence is manifest in a strong modification of $n({\bf k})$ in a small region below ${\bf k}_{_F}$, but a nearly $T$ independant $n({\bf k}_{_F})$.