Harvard Condensed Matter Theory Seminars

Victor Galitski, University of Maryland

Quantum Fluctuations in two-dimensional superconductors

In this talk, I will review recent theoretical and experimental results on quantum fluctuation effects in two-dimensional disordered superconductors. First, I will discuss a quantum version of the Gaussian Alsamazov-Larkin theory in the vicinity of the disorder-tuned and magnetic-field-tuned superconducting quantum critical point (QCP). It will be shown that the result for the leading quantum correction to conductivity may change sign at low temperature - a counter-intuitive result, which has been confirmed by experiment however. I will also argue that the fluctuation diamagnetism and Nernst effect are naturally very large near the superconducting transition and the corresponding parameters are expected to exceed the Fermi liquid values even in the perturbative regime. A complete theory of Gaussian superconducting fluctuations on the Nernst effect will be discussed. Next, I will talk about the recently developed microscopic non-perturbative theory of superconducting fluctuations near the disorder-tuned QCP, where one can get insight into the behavior of interacting fluctuating Cooper pairs in the Ginzburg fluctuation region. I will conclude by discussing the Griffiths effects of rare disorder fluctuations, which may smear out the quantum critical behavior.

Refs: Victor Galitski, Phys. Rev. Lett. 100, 127001 (2008); Phys. Rev. B 77, 100502(R) (2008)

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