Dynamical correlations in the spin-half two-channel Kondo model

TL;DR

This paper investigates the dynamical correlations in the spin-half two-channel Kondo model, analyzing how channel anisotropy and magnetic fields influence spectral functions and crossover behaviors between Fermi liquid and non-Fermi liquid regimes.

Contribution

It provides a conformal field theory-based scaling approach and numerical results that characterize the spectral functions and crossover regimes in the 2CK model under various perturbations.

Findings

Universal resonance in local fermion spectral function under small magnetic field

Boundaries of the 2CK scaling regime depend on perturbation type and operator

Dominant superconducting instability in the composite channel

Abstract

Dynamical correlations of various local operators are studied in the spin-half two-channel Kondo (2CK) model in the presence of channel anisotropy or external magnetic field. A conformal field theory-based scaling approach is used to predict the analytic properties of various spectral functions in the vicinity of the two-channel Kondo fixed point. These analytical results compare well with highly accurate density matrix numerical renormalization group results. The universal cross-over functions interpolating between channel-anisotropy or magnetic field-induced Fermi liquid regimes and the two-channel Kondo, non-Fermi liquid regimes are determined numerically. The boundaries of the real 2CK scaling regime are found to be rather restricted, and to depend both on the type of the perturbation and on the specific operator whose correlation function is studied. In a small magnetic field, a universal resonance is observed in the local fermion's spectral function. The dominant superconducting instability appears in the composite superconducting channel.