The interplay of interactions and disorder explored through fluctuating superconductors

Georg Schwiete, Mainz University

22.07.2014 at 09:00 

The influence of disorder on interacting many-body systems plays a prominent role in modern condensed matter physics. Not only is the presence of disorder often unavoidable in complex materials, disorder leads to fascinating phenomena in their own right. Generally speaking, disorder tends to slow down the motion of particles and even very weak disorder may completely localize them. The addition of interactions to the problem leads to a plethora of new phenomena.

In recent years, progress in fabrication and measurement techniques has lead to detailed experimental studies of fluctuation phenomena in low-dimensional superconductors. In this talk, I will discuss how superconducting fluctuations can increase the resistance of thin disordered films which are on the verge of becoming superconductors. In our theoretical studies on this subject we deviate from the traditional diagrammatic approach to the problem, which lead to conflicting results. Instead, we work with a quantum kinetic equation approach, which allows us to obtain results for the fluctuation conductivity in the entire normal-metal part of the phase diagram. This includes, in particular, the vicinity of the magnetic field-tuned quantum critical point. In this region of the phase diagram, close to the superconducting phase at low temperatures, experimental studies reveal a resistance maximum as a function of the magnetic field. Our calculations elucidate the physical mechanism underlying this fluctuation-induced increase of resistance.

G. Schwiete and Y. Oreg, Phys. Rev. Lett. 103, 037001 (2009); Phys. Rev. B 82, 214514 (2010): Fluctuation persistent currents in small superconducting rings.

K. S. Tikhonov, G. Schwiete, and A. M. Finkelstein, Phys. Rev. B 85, 174527 (2012); B. Tarasinski and G. Schwiete, Phys. Rev. B 88, 014518 (2013), and in preparation: Fluctuation conductivity in superconducting films, wires and cylinders.