Ground-State Properties of Extended Two-Channel Kondo Model

TL;DR

This paper investigates the ground-state properties of an extended two-channel Kondo model, revealing how the inclusion of a singlet state influences the stability of Fermi-liquid versus non-Fermi-liquid states, and maps out the phase diagram.

Contribution

It introduces an extended model with a localized singlet state and demonstrates its effect on ground-state stability, providing a qualitative phase diagram consistent with prior studies.

Findings

Channel exchange coupling via the singlet stabilizes the Fermi-liquid state.

The phase diagram aligns qualitatively with previous research.

A unique fixed point exists for both Fermi-liquid and non-Fermi-liquid states.

Abstract

Ground-state properties are examined for an extended two-channel Kondo model where the Hilbert space of the localized states is extended to include a singlet state in addition to the doublet states. By means of zero-th order variational wavefunctions with different symmetries, which are associated with the non-Fermi-liquid and the Fermi-liquid ground states, we demonstrate that the channel exchange coupling via the localized singlet state stabilizes the Fermi-liquid wavefunction. The ground-state phase diagrams, which are in qualitative agreement with the previous study performed by Koga and Shiba, are obtained. The comparison to the structure of the resultant wavefunctions suggests that a unique non-Fermi-liquid (Fermi-liquid) fixed point exists, irrespective of the localized ground state.