Quantum phase transitions in a charge-coupled Bose-Fermi Anderson model

Abstract

We study the competition between Kondo physics and dissipation within an Anderson model of a magnetic impurity level that hybridizes with a metallic host and is also coupled, via the impurity charge, to the displacement of a bosonic bath having a spectral density proportional to ω^s. As the impurity-bath coupling increases from zero, the effective Coulomb interaction between two electrons in the impurity level is progressively renormalized from its repulsive bare value until it eventually becomes attractive. For weak hybridization, this renormalization in turn produces a crossover from a conventional, spin-sector Kondo effect to a charge Kondo effect. At particle-hole symmetry, and for sub-Ohmic bath exponents 0 < s < 1, further increase of the impurity-bath coupling results in a continuous, zero-temperature transition to a broken-symmetry phase in which the ground-state impurity occupancy \n_d acquires an expectation value <\n_d>_0 \ne 1. The response of the impurity occupancy to a locally applied electric potential features the hyperscaling of critical exponents and ω/T scaling that are expected at an interacting critical point. The numerical values of the critical exponents suggest that the transition lies in the same universality class as that of the sub-Ohmic spin-boson model. For the Ohmic case s = 1, the transition is instead of Kosterlitz-Thouless type. Away from particle-hole symmetry, the quantum phase transition is replaced by a smooth crossover, but signatures of the symmetric quantum critical point remain in the physical properties at elevated temperatures and/or frequencies.

26 pages, 31 figures. Added references and corrected typos

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Cited by in corpus (8)

• The mass-flow error in the Numerical Renormalization Group method and the critical behavior of the sub-ohmic spin-boson model
• Numerical Renormalization Group for the sub-ohmic spin-boson model: A conspiracy of errors
• Tunable Quantum Phase Transitions in a Resonant Level Coupled to Two Dissipative Baths
• Transport Signatures of Majorana Quantum Criticality Realized by Dissipative Resonant Tunneling
• Critical charge fluctuations in a pseudogap Anderson model
• Quantum phase transition of the sub-Ohmic rotor model
• Nonequilibrium occupation number and charge susceptibility of a resonance level close to a dissipative quantum phase transition
• No spin-localization phase transition in the spin-boson model without local field