Superfluid stiffness renormalization and critical temperature enhancement in a composite superconductor
Prof. Dror Orgad, Hebrew University
12/12/2013 - 12:30 - 13:30
Seminar room 210, Reznick, bld 209
Increasing superconductors' critical temperature has been a long standing goal in material science.
In order to do so, both a high Cooper pairing energy and a large phase coherence of the pairs are required.
Unfortunately, systems in which pairing is strong typically do not exhibit a correspondingly high transition
temperature due to their susceptibility to large phase fluctuations. Conversely, large phase stiffness is a
property of all simple metals, but these typically have (at best) weak pairing. It has been suggested that it
is possible to overcome this tension by coupling a superconductor to a metallic layer. We consider a model
of such a composite system, and determine its critical temperature using a combination of analytic and
Monte Carlo methods. We find that the maximal critical temperature is bounded from above when the pairing
is strong, and scales like a fraction of the zero temperature pairing gap when the pairing is weak. In this
weak pairing regime the critical temperature seems to exceed that of a homogeneous model of
the same pairing energy.