Quantum criticality out of equilibrium in the pseudogap Kondo model

Chung-Hou Chung*, Kenneth Yi Jie Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Quantum phase transitions out of equilibrium are outstanding emergent subjects in condensed matter physics with great fundamental importance and challenges. We theoretically investigate here the nonequilibrium quantum phase transition in a generic nano-setup: the pseudogap Kondo model where a Kondo quantum dot couples to two-left (L) and right (R)-voltage-biased fermionic leads with power-law density of states (DOS) with respect to their Fermi levels μ L/R, ρ c,L(R)(ω) ∞ |ω -μ L( R) |r with 0<r<1. In equilibrium (μ L- μ R=0) and for 0<r<1/2, with increasing Kondo correlations this model exhibits a quantum phase transition from a unscreened local moment (LM) phase to the Kondo screened phase. At finite bias voltages and near criticality, we discover new nonequilibrium universal scaling behaviors in conductance, conduction electron T matrix, and local spin susceptibility via a controlled frequency-dependent renormalization group (RG) approach. The current-induced decoherence is key to understanding these distinct universal nonequilibrium quantum critical regimes. The relevance of our results to experiment is discussed.

Original languageEnglish
Article number195106
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number19
StatePublished - 3 May 2012

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