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R. G. Herb Condensed Matter Seminar
Precision Measurements of the London Penetration Depth and Pairing Symmetry in Superconductors
Date: Thursday, February 12th
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Ruslan Prozorov, Iowa State University & Ames Laboratory
Abstract: The pairing mechanism is the Holy Grail for researchers in the field of superconductivity. One of the experimentally accessible manifestations of the pairing mechanism is the structure of the superconducting gap on the Fermi surface and the corresponding behavior of low-energy quasiparticles with respect to an applied magnetic field, scattering rate, heat flow, etc. The London penetration depth is directly related to the superfluid density and, therefore, is one of the primary experimentally measurable quantities. It is also relatively easy to model for various superconducting gaps and for arbitrary scattering by using microscopic or semiclassical formalisms.

During the last 20 years, there has been remarkable progress in the development of techniques for ultra-precise measurements of the penetration depth, especially in the frequency-domain. I will briefly review the major milestones where this technique has been used--from the very first discovery of d-wave pairing in hole-doped cuprates [1] through d-wave pairing in electrondoped cuprates [2]. I will spend most of the time on today's hot topic of Fe-based pnictide superconductors for which the unconventional behavior will be demonstrated [3]. It is possible that this class of materials is one of the most complex we have ever encountered in the field of superconductivity due to complex multi-band electronic structure and substantial influence of the magnetic subsystem.

[1] W. N. Hardy et al., Phys. Rev. Lett. 70, 3999 (1993)
[2] R. Prozorov et al., Phys. Rev. Lett. 85, 3700 (2000)
[3] R. T. Gordon et al., http://arxiv.org/abs/0812.3683
Host: Andrey Chubukov
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