Fluctuation spectroscopy of disordered two-dimensional superconductors

A. Glatz; A. A. Varlamov; V. M. Vinokur

doi:10.1103/PhysRevB.84.104510

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Fluctuation spectroscopy of disordered two-dimensional superconductors

A. Glatz, A. A. Varlamov, V. M. Vinokur

DOI 10.1103/PhysRevB.84.104510 · Physical Review B

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Abstract

We revise the long-studied problem of fluctuation conductivity (FC) in disordered two-dimensional superconductors placed in a perpendicular magnetic field by finally deriving the complete solution in the temperature-magnetic field phase diagram. The obtained expressions allow both to perform straightforward (numerical) calculation of the FC surface δσxx(tot)(T,H) and to get asymptotic expressions in all its qualitatively different domains. This surface becomes in particular nontrivial at low temperatures, where it is trough-shaped with δσxx(tot)(T,H)<0. In this region, close to the quantum-phase transition, δσxx(tot)(T,H=const) is nonmonotonic, in agreement with experimental findings. We reanalyzed and present comparisons to several experimental measurements. Based on our results we derive a qualitative picture of superconducting fluctuations close to Hc2(0) and T=0 where fluctuation Cooper pairs rotate with cyclotron frequency ωc∼ΔBCS−1 and Larmor radius ∼ξBCS, forming some kind of quantum liquid with long coherence length ξQF≫ξBCS and slow relaxation (τQF≫ℏΔBCS−1).