Quantum criticality and superconducting gap evolution in Fe-based superconductors

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Date/Time:Thursday, 25 Oct 2012 - Saturday, 27 Oct 2012
Location:PHYSICS Hall Room 5
Channel:Condensed Matter Physics
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Kyuil Cho
Ames Laboratory
Iowa State University

The quantum critical point (QCP), where the transitions occur at absolute zero temperature due to quantum fluctuation, usually induces a new phase such as unconventional superconductivity. Whether the QCP still exists beneath the superconducting phase was a long-standing question, but very hard task since most of physical and magnetic properties are not useful inside of the superconducting phase. Here we present the zero-temperature penetration depth measurement in

BaFe2(As1-x,Px)2 by using two combined techniques (tunnel diode resonator + Al coating). The result shows a sharp peak at the optimal doping (x = 0.3) which identifies the existence of the QCP beneath the superconducting dome [1]. In addition, the doping dependent penetration depth studies in various Fe-based superconductors reveal that the superconducting gap structure shows a universal dome-like evolution as the dopant concentration increases. The details of experimental and theoretical consideration will be discussed.

[1] K. Hashimoto, Kyuil Cho, et al., Science 336, 1554 (2012).