Large-N Approach to the Two-Channel Kondo Lattice

TL;DR

This paper explores the large-N limit of the two-channel Kondo lattice, revealing spontaneous channel symmetry breaking, emergent order fractionalization, and topological defects affecting the phase diagram.

Contribution

It introduces the concept of order fractionalization in the two-channel Kondo lattice and derives an effective action describing symmetry breaking and collective modes.

Findings

Spontaneous channel symmetry breaking forms a channel ferromagnet.

Topological defects carry U(1) flux affecting electron phases.

Phase diagram includes a non-magnetic transition between different Fermi surface sizes.

Abstract

This paper studies the two-channel Kondo lattice in the large-N limit at half-filling. In this model, the continuous channel-symmetry is spontaneously broken, forming a channel ferromagnet in which one conduction channel forms a Kondo insulator, while the other remains conducting. The paper discusses how this ground-state can be understood using the concept of "order fractionalization", in which the channel magnetization breaks up into an emergent spinor order parameter. By integrating out the fermions we derive an effective action that describes this symmetry breaking and its emergent collective modes. A remarkable observation is that topological defects in the order parameter carry a U(1) flux, manifested in the Aharonov-Bohm phase picked by electrons that orbit the defect. By studying the effective action, we argue that the phase diagram contains a non-magnetic transition between a large and a small Fermi surface.