Phase transition in the one-dimensional Kondo lattice model with attractive electron-electron interaction

TL;DR

This paper investigates the phase transitions in a one-dimensional Kondo lattice model with attractive electron-electron interactions at half-filling, revealing three distinct phases with different spin and charge excitation properties.

Contribution

It provides a comprehensive phase diagram and characterization of phases using density matrix renormalization group methods, including analysis of gapped and gapless states.

Findings

Identification of three distinct phases depending on coupling constants.

Two phases exhibit spin and charge gaps with different excitation spectra.

One phase is gapless with quasi long-range order in spin and charge densities.

Abstract

The one-dimensional Kondo lattice model with attractive interaction among the conduction electrons is analyzed in the case of half-filling. It is shown that there are three distinct phases depending on the coupling constants of the model. Two phases have a spin and charge gap. While one shows a clear separation of the spin and charge excitation spectrum the other phase may be characterized as a band insulator type where both excitations are due to two-particle states. The third phase is gapless in both channels and has quasi long-range order in the spin and charge density wave correlation. In this phase the spin and charge excitations have again a clearly separated spectrum. For the analysis we discuss first two limiting cases. Then a density matrix renormalization group calculation on finite systems is applied to determine the phase diagram and the correlation functions in the gapped and gapless phase for general couplding constants.