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Heat Transport as a Probe of Superconducting Gap Structure

Journal Article · · New Journal of Physics
OSTI ID:1040124
The structure of the superconducting gap provides important clues on the symmetry of the order parameter and the pairing mechanism. The presence of nodes in the gap function imposed by symmetry implies an unconventional order parameter, other than s-wave. Here we show how measurements of the thermal conductivity at very low temperature can be used to determine whether such nodes are present in a particular superconductor, and shed light on their nature and location. We focus on the residual linear term at T {yields} 0. A finite value in zero magnetic field is strong evidence for symmetry-imposed nodes, and the dependence on impurity scattering can distinguish between a line of nodes or point nodes. Application of a magnetic field probes the low-energy quasiparticle excitations, whether associated with nodes or with a small value of the gap on some part of the Fermi surface, as in a multi-band superconductor. We frame our discussion around archetypal materials: Nb for s-wave, Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} for d-wave, Sr{sub 2}RuO{sub 4} for p-wave, and NbSe{sub 2} for multi-band superconductivity. In that framework, we discuss three heavy-fermion superconductors: CeIrIn{sub 5}, CeCoIn{sub 5} and UPt{sub 3}.
Research Organization:
BROOKHAVEN NATIONAL LABORATORY (BNL)
Sponsoring Organization:
USDOE SC OFFICE OF SCIENCE (SC)
DOE Contract Number:
AC02-98CH10886
OSTI ID:
1040124
Report Number(s):
BNL--90334-2009-JA; KC0202010
Journal Information:
New Journal of Physics, Journal Name: New Journal of Physics Vol. 11
Country of Publication:
United States
Language:
English