Vortices in dirty superconducting films

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Date/Time:Thursday, 02 Mar 2017 from 4:10 pm to 5:00 pm
Location:Physics 3
Phone:515-294-7377
Channel:College of Liberal Arts and Sciences
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Elio Koenig-Tarasevich, Rutgers University

My talk is devoted to the long standing question of superconductivity in dirty two dimensional samples. In a first, introductory part I will review exemplary experiments and summarize theories put forward within the two main paradigms dubbed ,,bosonic" and ,,fermionic" approach, respectively.

In the second part of the talk I will present our recent theory for the finite temperature vortex-unbinding transition in homogeneously disordered superconducting films. This theory incorporates the effects of quantum, mesoscopic, and thermal fluctuations stemming from length scales ranging from the superconducting coherence length down to the Fermi wavelength. This allows us to determine the dependence of essential observables (including the vortex-unbinding temperature, the superconducting density, as well as the temperature-dependent resistivity and thermal conductivity) on microscopic characteristics such as the disorder-induced scattering rate and bare interaction couplings.

The third and last part of the talk is dedicated to the voltage generation in 2D superconducting films of finite width (strips) at zero temperature and subjected to a finite current bias. Our approach is based on the long-distance theory which only involves fluctuations of the condensate's phase and of electromagnetic fields. In this context, we show by means of a variational Ansatz that the voltage is generated by multi-vortex configurations (instead of single or double vortex configurations considered previously). At the border of its applicability, our theory also evidences the superconductor-insulator quantum phase transition. Using the BCS theory of dirty superconductors as an input for our phenomenological parameters, this transition is shown to occur close to (but above) g ~ 1, where g is the dimensionless normal state conductance.