Merging of single-particle levels and non-Fermi-liquid behavior of finite Fermi systems

TL;DR

This paper explores how merging of single-particle energy levels in finite Fermi systems leads to non-Fermi-liquid behavior, significantly altering quasiparticle properties across various quantum many-body systems.

Contribution

It demonstrates that level merging is a common phenomenon in finite Fermi systems, challenging the traditional quasiparticle framework.

Findings

Level merging causes nonintegral quasiparticle occupations

The phenomenon is widespread in quantum many-body systems

Implications for nuclear, atomic, and solid-state physics

Abstract

We examine the problem of finite Fermi systems having a degenerate single-particle spectrum and show that the Landau approach, applied to such a system, admits the possibility of merging single-particle levels. It is demonstrated that the opportunity for this behavior is widespread in quantum many-body systems. The salient feature of the phenomenon is the occurrence of nonintegral quasiparticle occupation numbers, leading to a radical alteration of the standard quasiparticle picture. Implications of this alteration are considered for nuclear, atomic, and solid-state systems.