Seminar on Disorder and strong electron correlations: " Quantum Fluctuations and Dynamic Clustering of Fluctuating Cooper Pairs "
(Universita' di Roma II, CNR-SPIN, Roma)
We derive the exact expressions for the fluctuation conductivity in two dimensional superconductors as a function of temperature and magnetic field in the whole phase diagram above the upper critical field line Hc2(T). Focusing on the vicinity of the quantum phase transition near zero temperature we arrive to the conclusion that as the magnetic field approaches the critical field Hc2(0) from above, a peculiar dynamic state consisting of clusters of coherently rotating fluctuation Cooper-pairs forms. We estimate the characteristic size QF( H) and lifetime QF( H) of such clusters and indicate in the corresponding domain of the phase diagram, where such phenomenon can be observed. The derived values QF( H) and QF( H) allow us to reproduce qualitatively the available results for the quantum fluctuation contributions to the in-plane conductivity, magnetization, and the Nernst coefficient. Finally we predict the existence of a peak in the zero temperature transverse magneto-conductivity of layered superconductors at fields above Hc2(0).
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