Superfluid stiffness renormalization and critical temperature enhancement in a composite superconductor

Speaker
Prof. Dror Orgad, Hebrew University
Date
12/12/2013 - 15:30 - 14:30Add to Calendar 2013-12-12 14:30:00 2013-12-12 15:30:00 Superfluid stiffness renormalization and critical temperature enhancement in a composite superconductor 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. Seminar room 210, Reznick, bld 209 המחלקה לפיזיקה physics.dept@mail.biu.ac.il Asia/Jerusalem public
Place
Seminar room 210, Reznick, bld 209
Abstract
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.

תאריך עדכון אחרון : 04/12/2013