Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 45: Superconductivity: (General) Theory

TT 45.5: Talk

Wednesday, March 13, 2013, 16:00–16:15, H21

Effects of randomness on the critical temperature in quasi-1D and quasi-2D superconductors — •Enver Nakhmedov^1,2, Oktay Alekperov², and Reinhold Oppermann¹ — ¹Institut für Theoretische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany — ²Institute of Physics, Azerbaijan National Academy of Sciences, H. Cavid str. 33, AZ1143 Baku, Azerbaijan

Effects of non-magnetic disorder on the critical temperature Tc and on diamagnetism of quasi-1D and quasi-2D superconductors (SCs) are reported. The organic SCs are modeled as superconducting wires or layers connecting each others through the Josephson coupling. The Josephson energy is considered to be random parameter with Gaussian distribution. The phase of the order parameter is averaged over thermodynamic fluctuations as well as over disorder by employing the replica method. We show that the randomness destroys phase coherence between wires in quasi-1D SCs and that Tc vanishes discontinuously at a critical disorder-strength. Nevertheless the disorder of arbitrary high strength in quasi-2D organic SCs can not destroy completely the superconducting phase. The interplay between disorder and quantum phase fluctuations is shown to result in quantum critical behavior at T=0 in quasi-1D SCs, which manifests itself as a superconducting-normal metal phase transition of first-order at a critical disorder strength. The parallel and transverse components of the penetration-depth are evaluated. They diverge at different critical temperatures, which correspond to pair-breaking and phase-coherence breaking respectively. Our theory agrees well with the experimental measurements.