Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 99: Superconductivity: (General) Theory 2

TT 99.5: Talk

Thursday, March 19, 2015, 16:00–16:15, H 2053

Conformal phase transition as a new perspective on conventional superconductors — •Flavio Nogueira¹ and Asle Sudbo² — ¹Theoretische Physik III, Ruhr-Universität Bochum — ²Dept. of Physics, Norwegian University of Science and Technology

We argue that the phase transition in strong type I superconductors features charged fluctuations, meaning that it is essentially driven by thermal fluctuations of the magnetic field. This is simply a consequence of the small value of the Ginzburg parameter in the deep type I regime. We substantiate this conclusion by a generalization of the Ginzburg criterion to include charged fluctuations. Finally, we demonstrate by means of a renormalization group analysis that the correlation length actually does not obey a power law as function of T−T_c. Rather it features an essential singularity at T_c, which is characteristic of a so called conformal phase transition, one known example of it being the Berezinski-Kosterliz-Thouless (BKT) phase transition in two-dimensional superfluids. We argue that a similar behavior happens in three-dimensional strongly type I superconductors. One important prediction from our theory that may be tested experimentally by microwave measurement is a universal discontinuous jump in the superfluid density.