Diagonal composite order in two-channel Kondo lattice

TL;DR

This paper reports a new type of symmetry breaking in the two-channel Kondo lattice, revealing a composite odd-frequency order associated with orbital-selective Kondo effects, using advanced quantum Monte Carlo and dynamical mean-field theory methods.

Contribution

It introduces a novel composite order parameter for the two-channel Kondo lattice, demonstrating a unique odd-frequency orbital order not previously identified.

Findings

Spontaneous orbital symmetry breaking observed

Orbital-selective Kondo insulating behavior identified

First example of odd-frequency composite order

Abstract

A novel type of symmetry breaking is reported for the two-channel Kondo lattice where conduction electrons have spin and orbital (channel) degrees of freedom. Using the continuous-time quantum Monte Carlo and the dynamical mean-field theory, a spontaneous breaking of the orbital symmetry is observed. The tiny breakdown of orbital occupation number, however, vanishes if the conduction electrons have the particle-hole symmetry. The proper order parameter instead is identified as a composite quantity representing the orbital-selective Kondo effect. The single-particle spectrum of the selected orbital shows insulating property, while the other orbital behaves as Fermi liquid. This composite order is the first example of odd-frequency order other than off-diagonal order (superconductivity), and is a candidate of hidden order in $f$-electron systems.