Critical field theory of the Kondo lattice model in two dimensions

TL;DR

This paper develops a critical field theory for the two-dimensional Kondo lattice model, revealing emergent gauge fields and non-Fermi liquid behavior near the quantum critical point.

Contribution

It introduces a new emergent U(1) gauge field arising from critical Kondo singlet fluctuations, distinct from the slave boson gauge field, and derives a low-energy effective theory.

Findings

Non-Fermi liquid temperature dependence of specific heat.

Non-Fermi liquid behavior in electron self-energy.

Emergence of a new U(1) gauge field at the quantum critical point.

Abstract

In the context of the U(1) slave boson theory we derive a critical field theory near the quantum critical point of the Kondo lattice model in two spatial dimensions. First we argue that strong gauge fluctuations in the U(1) slave boson theory give rise to confinement between spinons and holons, thus causing "neutralized" spinons in association with the slave boson U(1) gauge field. Second we show that critical fluctuations of Kondo singlets near the quantum critical point result in a new U(1) gauge field. This emergent gauge field has nothing to do with the slave boson U(1) gauge field. Third we find that the slave boson U(1) gauge field can be exactly integrated out in the low energy limit. As a result we find a critical field theory in terms of renormalized conduction electrons and neutralized spinons interacting via the new emergent U(1) gauge field. Based on this critical field theory we obtain the temperature dependence of specific heat and the imaginary part of the self-energy of the renormalized electrons. These quantities display non-Fermi liquid behavior near the quantum critical point.