One-Dimensional Kondo Lattice at Half Filling: Charge Properties

TL;DR

This paper investigates the charge and optical properties of a one-dimensional Kondo lattice at half filling, revealing how instanton effects influence the optical conductivity and relate to topological charges in the system.

Contribution

It demonstrates the impact of instanton effects on the charge sector and optical conductivity in a half-filled Kondo chain with degenerate conduction bands.

Findings

Optical conductivity at wave vector π is linked to topological charge density.

Gap or pseudogap in optical conductivity depends on the relation between M and 2S.

Charge current density at large wave vector is proportional to topological charge density.

Abstract

The model of Kondo chain with $M$-fold degenerate band of conduction electrons of spin 1/2 at half filling interacting with localized spins $S$ is studied. It is shown that due to the instanton effects the spin sector reveals itself in optical conductivity. Namely, the density of the charge current at large wave vector $k \approx \pi$ is proportional to the density of topological charge of the staggered magnetization. As a consequence, the optical conductivity at $k = \pi$ would either have a gap equal to three spin gaps (for $|M - 2S| = $(even) when the spin spectrum is gapful), or show a psedogap $\sigma(\omega, k = \pi) \sim \omega^2$ for $|M - 2S|$ = (odd).