Browsing by Subject "NOISE"

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    Nonequilibrium quantum transport through a dissipative resonant level
    (Physical Review B - Condensed Matter and Materials Physics, 2013-06-21) Chung, CH; Le Hur, K; Finkelstein, G; Vojta, M; Wölfle, P
    The resonant-level model represents a paradigmatic quantum system which serves as a basis for many other quantum impurity models. We provide a comprehensive analysis of the nonequilibrium transport near a quantum phase transition in a spinless dissipative resonant-level model, extending earlier work. A detailed derivation of a rigorous mapping of our system onto an effective Kondo model is presented. A controlled energy-dependent renormalization-group approach is applied to compute the nonequilibrium current in the presence of a finite bias voltage V. In the linear-response regime V→0, the system exhibits as a function of the dissipative strength a localized-delocalized quantum transition of the Kosterlitz-Thouless (KT) type. We address fundamental issues of the nonequilibrium transport near the quantum phase transition: Does the bias voltage play the same role as temperature to smear out the transition? What is the scaling of the nonequilibrium conductance near the transition? At finite temperatures, we show that the conductance follows the equilibrium scaling for VT. We furthermore provide different signatures of the transition in the finite-frequency current noise and ac conductance via a recently developed functional renormalization group (FRG) approach. The generalization of our analysis to nonequilibrium transport through a resonant level coupled to two chiral Luttinger liquid leads, generated by fractional quantum Hall edge states, is discussed. Our work on the dissipative resonant level has direct relevance to experiments on a quantum dot coupled to a resistive environment, such as H. Mebrahtu,. © 2013 American Physical Society.
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    Phase diffusion in graphene-based Josephson junctions.
    (Physical review letters, 2011-09-21) Borzenets, IV; Coskun, UC; Jones, SJ; Finkelstein, G
    We report on graphene-based Josephson junctions with contacts made from lead. The high transition temperature of this superconductor allows us to observe the supercurrent branch at temperatures up to ∼2 K, at which point we can detect a small, but nonzero, resistance. We attribute this resistance to the phase diffusion mechanism, which has not been yet identified in graphene. By measuring the resistance as a function of temperature and gate voltage, we can further characterize the nature of the electromagnetic environment and dissipation in our samples.
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    Validation of algorithmic CT image quality metrics with preferences of radiologists
    (MEDICAL PHYSICS, 2019-11-01) Cheng, Yuan; Abadi, Ehsan; Smith, Taylor Brunton; Ria, Francesco; Meyer, Mathias; Marin, Daniele; Samei, Ehsan