2021/07/30 by Gu Zhang, E. Novais, Harold U. Baranger
Physics and Astronomy · #Condensed matter physics #Conductance #Crossover #Dissipative system #Fermi liquid theory #Luttinger liquid #Non-equilibrium thermodynamics #Physics #Physics of Superconductivity and Magnetism #Quantum #Quantum and electron transport phenomena #Quantum critical point #Quantum many-body systems #Quantum mechanics #Quantum phase transition #Quantum tunnelling #Superconductivity #cond-mat.mes-hall #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.104.165423
published as Phys. Rev. B 104, 165423 (2021) · 18 pages. Accepted version: small corrections and improvements from v1
openalex publication_date 2021/10/25 · arxiv created 2022/03/14 · arxiv updated 2022/03/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We find the nonlinear conductance of a dissipative resonant level in the nonequilibrium steady state near its quantum critical point. The system consists of a spin-polarized quantum dot connected to two resistive leads that provide ohmic dissipation. We focus on the crossover from the strong-coupling, non-Fermi-liquid regime to the weak-coupling, Fermi-liquid ground state, a crossover driven by the instability of the quantum critical point to hybridization asymmetry or detuning of the level in the dot. We show that the crossover properties are given by tunneling through an effective single barrier described by the boundary sine-Gordon model. The nonlinear conductance is then obtained from thermodynamic Bethe ansatz results in the literature, which were developed to treat tunneling in a Luttinger liquid. The current-voltage characteristics are thus found for any value of the resistance of the leads. For the special case of lead resistance equal to the quantum resistance, we find mappings onto, first, the two-channel Kondo model and, second, an effectively noninteracting model from which the nonlinear conductance is found analytically. A key feature of the general crossover function is that the nonequilibrium crossover driven by applied bias is different from the crossover driven by temperature -- we find that the nonequilibrium crossover is substantially sharper. Finally, we compare to experimental results for both the bias and temperature crossovers: the agreement is excellent.