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Louis TAILLEFER - Université de Sherbrooke

The gap structure of the putative p-wave superconductor Sr2RuO4

There is strong experimental evidence that the superconductor Sr2RuO4 has a chiral p-wave order parameter [1,2]. If so, symmetry does not require that the associated gap has nodes, yet specific heat [3], ultrasound [4] and thermal conductivity [5] measurements establish the existence of line nodes in the superconducting gap structure of Sr2RuO4. Theoretical scenarios have been proposed to account for the existence of accidental nodes within a p-wave state [6-9]. To examine such scenarios, it is essential to know whether the line nodes are vertical (parallel to the tetragonal c axis) or horizontal (perpendicular to the c axis).

I will report thermal conductivity measurements on high-quality single crystals of Sr2RuO4 down to 50 mK for currents parallel and perpendicular to the c axis. We find that there is no quasiparticle transport along the c axis in the T = 0 limit, in contrast with the large residual conductivity found in the basal plane. The immediate interpretation of this a-c anisotropy is that the line of nodes in Sr2RuO4 is horizontal. We discuss the implications of this finding and compare our data with similar data on the heavy-fermion superconductor CeIrIn5.

[1] Maeno et al., Journal of the Physical Society of Japan 81, 011009 (2012).

[2] Kallin, Reports on Progress in Physics 75, 042501 (2012).

[3] Nishizaki et al., Journal of Low temperature Physics 117, 1581 (1999).

[4] Lupien et al., Physical Review Letters 86, 5986 (2001).

[5] Suzuki et al., Physical Review Letters 88, 227004 (2002).

[6] Nomura, Journal of the Physical Society of Japan 74, 1818 (2005).

[7] Raghu et al., Physical Review Letters 105, 136401 (2010).

[8] Wang et al., Europhysics Letters 104, 17013 (2013).

[9] Scaffidi et al., Physical Review B 89, 220510 (2014).


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