Faithful fermionic representations of the Kondo lattice model

TL;DR

This paper introduces a new fermionic representation of the Kondo lattice model using canonical transformations, enabling unconstrained fermionic descriptions and revealing a gapped spin liquid phase.

Contribution

It presents a novel fermionic representation that is faithful and constraint-free, including an O(3)-symmetric Majorana fermion formulation for the Kondo lattice model.

Findings

Identifies a new O(3)-symmetric Majorana fermion representation.

Proposes a natural trial state characterized as a gapped spin liquid.

Provides mean field analysis of the interacting fermionic theories.

Abstract

We study the Kondo lattice model using a class of canonical transformations that allow us to faithfully represent the model entirely in terms of fermions without constraints. The transformations generate interacting theories that we study using mean field theory. Of particular interest is a new manifestly O(3)-symmetric representation in terms of Majorana fermions at half-filling on bipartite lattices. This representation suggests a natural O(3)-symmetric trial state that is investigated and characterized as a gapped spin liquid.