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Hidden d-wave orbital triplet behind s± superconductivity in Fe-based superconductors

Speaker: 
T. Tzen Ong
Date: 
Mon, 23/09/2013 - 11:00am to 12:00pm
Location: 
S13-M01-11 (Physics Conference Room)
Host: 
Antonio Castro Neto
Event Type: 
Seminars

Abstract

A key issue in understanding the high temperature iron-based superconductors concerns the mechanism by which the paired electrons minimize their strong mutual Coulomb repulsion. Whereas electronically paired superconductors generally avoid the Coulomb interaction through the formation of higher angular momentum pairs, iron based superconductors involve s-wave (s±) pairs with zero angular momentum. By taking into account the orbital degrees of freedom of the iron atoms, here we show that the s± pairs in these materials possess hidden d-wave symmetry, forming orbital triplets in which the d-wave angular momentum of the pairs is compensated by the internal angular momentum of the orbitals. The recent observation of a gap with octahedral structure in KFe2As2 materials[2] can be understood as a transition to a “high spin” configuration of the d-wave orbital triplets, through the alignment of the two angular momentum components of the pair.

1. T. Tzen Ong & P. Coleman, arXiv:1303.6325, T. Tzen Ong, P. Coleman & Joerg Schmalian, In preparation.
2. Okazaki, Shin et. al., Science 337, 1314 (2012)

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