Quantum criticality of the two-channel pseudogap Anderson model: Universal scaling in linear and non-linear conductance

TL;DR

This paper investigates the quantum critical behavior of a two-channel pseudogap Anderson model, revealing universal scaling laws in conductance at the phase transition between the two-channel Kondo and local moment phases.

Contribution

It provides the first detailed analysis of both linear and non-linear conductance scaling near the quantum critical point in a pseudogap Anderson model.

Findings

Universal scaling functions for conductance at criticality

Distinct critical exponents for linear and non-linear conductance

Implications for non-equilibrium quantum criticality

Abstract

The quantum criticality of the two-lead two-channel pseudogap Anderson model is studied. Based on the non-crossing approximation, we calculate both the linear and nonlinear conductance of the model at finite temperatures with a voltage bias and a power-law vanishing conduction electron density of states, $\propto |\omega-\mu_F|^r$ ($0<r<1$) near the Fermi energy. Equilibrium and non-equilibrium quantum critical properties at the two-channel Kondo (2CK) to local moment (LM) phase transition are addressed by extracting universal scaling functions in both linear and non-linear conductances, respectively. Clear distinctions are found on the critical exponents between linear and non-linear conductance. The implications of these two distinct quantum critical properties for the non-equilibrium quantum criticality in general are discussed.