Transitions from small to large Fermi momenta in a one-dimensional Kondo lattice model

TL;DR

This paper investigates continuous quantum phase transitions involving changes in Fermi momentum in a one-dimensional Kondo lattice model, revealing new critical behaviors influenced by spin anisotropy and frustration.

Contribution

It demonstrates the existence of continuous Fermi-momentum-changing transitions in a 1D Kondo lattice, including effects of spin anisotropy and frustration, which were previously unexplored.

Findings

Continuous transitions between small and large Fermi momentum phases.

Spin anisotropy enables a smooth Fermi-momentum change.

Frustration leads to coexistence regions between phases.

Abstract

We study a one-dimensional system that consists of an electron gas coupled to a spin-1/2 chain by Kondo interaction away from half-filling. We show that zero-temperature transitions between phases with "small" and "large" Fermi momenta can be continuous. Such a continuous but Fermi-momentum-changing transition arises in the presence of spin anisotropy, from a Luttinger liquid with a small Fermi momentum to a Kondo-dimer phase with a large Fermi momentum. We have also added a frustrating next-nearest-neighbor interaction in the spin chain to show the possibility of a similar Fermi-momentum-changing transition, between the Kondo phase and a spin-Peierls phase, in the spin isotropic case. This transition, however, appears to involve a region in which the two phases coexist.