title: Quantum criticality of the two-channel pseudogap Anderson model: universal scaling in linear and non-linear conductance.
abstract: The quantum criticality of the two-lead two-channel pseudogap Anderson impurity model is studied. Based on the non-crossing approximation (NCA) and numerical renormalization group (NRG) approaches, 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, ρc(ω) proportional |ω − μF|(r) (0 < r < 1) near the Fermi energy μF. At a fixed lead-impurity hybridization, a quantum phase transition from the two-channel Kondo (2CK) to the local moment (LM) phase is observed with increasing r from r = 0 to r = rc < 1. Surprisingly, in the 2CK phase, different power-law scalings from the well-known [Formula: see text] or [Formula: see text] form is found. Moreover, novel power-law scalings in conductances at the 2CK-LM quantum critical point are identified. Clear distinctions are found on the critical exponents between linear and non-linear conductance at criticality. The implications of these two distinct quantum critical properties for the non-equilibrium quantum criticality in general are discussed.
authors.affiliation: Electrophysics Department, National Chiao-Tung University, HsinChu, Taiwan, 300, Republic of China.
authors.forename: Tsan-Pei
authors.initials: TP
authors.lastname: Wu
authors.forename: Xiao-Qun
authors.initials: XQ
authors.lastname: Wang
authors.forename: Guang-Yu
authors.initials: GY
authors.lastname: Guo
authors.forename: Frithjof
authors.initials: F
authors.lastname: Anders
authors.forename: Chung-Hou
authors.initials: CH
authors.lastname: Chung