Spin degrees of freedom and flattening of the spectra of single-particle excitations in strongly correlated Fermi systems

TL;DR

This paper investigates how long-range spin-spin correlations influence the flat regions in single-particle spectra of strongly correlated Fermi systems, revealing the effects of spin-dependent forces on spectral flattening and magnetization.

Contribution

It extends the Nozieres model by including spin-dependent long-range forces and analyzes their impact on spectral flattening and spontaneous magnetization.

Findings

Long-range spin correlations affect the flat spectral regions.

Sign change in spin-dependent force induces spontaneous magnetization.

Increasing force strength shrinks and eventually eliminates the flat spectral domain.

Abstract

The impact of long-range spin-spin correlations on the structure of a flat portion in single-particle spectra $\xi(p)$, which emerges beyond the point, where the Landau state loses its stability, is studied. We supplement the well-known Nozieres model of a Fermi system with limited scalar long-range forces by a similar long-range spin-dependent term and calculate the spectra versus its strength $g$. It is found that Nozieres results hold as long as $g>0$. However, with $g$ changing its sign, the spontaneous magnetization is shown to arise at any nonzero $g$. The increase of the strength $|g|$ is demonstrated to result in shrinkage of the domain in momentum space, occupied by the flat portion of $\xi(p)$, and, eventually, in its vanishing.