Pairing symmetry in KFe2As2, RbFe2As2, and CsFe2As2

Speaker: 
Fazel Fallah Tafti, Princeton University
Event Date and Time: 
Mon, 2015-06-08 11:00 - 12:00
Location: 
AMPEL 311
Intended Audience: 
Graduate

The discovery of iron-based superconductors sparked a tremendous amount of excitement in finding a new family of high Tc superconductors next to cuprates. A well-established result is that the pairing symmetry of iron-based superconductors is s-wave, setting them apart from the d-wave cuprates. An intriguing question remains as to whether d-wave can ever become a dominant pairing channel in iron-based superconductors. Through a series of thermal conductivity measurements, we observe strong evidence for d-wave pairing in an iron-based superconductor KFe2As2 (Tc ~ 4 K). In this talk, I will present thermal conductivity data that point towards d-wave pairing in KFe2As2 and related materials RbFe2As2 and CsFe2As2. Theoretical calculations show that d-wave and s-wave pairing are closely competing in these fully hole-doped iron-pnictides. I will show that as a function of pressure, the superconducting phase of KFe2As2, RbFe2As2, and CsFe2As2 go through a drastic change reflected in a “V” shape pressure dependence of Tc as a function of pressure as well as a two-fold jump in Hc2 at a critical pressure. These experimental results highlight the tunable nature of superconductivity in (K,Rb,Cs)Fe2As2 and establish them as the link between iron-based and copper-based superconductors.

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