Superconducting Gap Structure of Spin-Triplet SuperconductorSr2RuO4Studied by Thermal Conductivity

Abstract

To clarify the superconducting gap structure of the spin-triplet superconductor Sr2RuO4, the in-plane thermal conductivity has been measured as a function of relative orientations of the thermal flow, the crystal axes, and a magnetic field rotating within the 2D RuO2 planes. The in-plane variation of the thermal conductivity is incompatible with any model with line nodes vertical to the 2D planes and indicates the existence of horizontal nodes. These results place strong constraints on models that attempt to explain the mechanism of the triplet superconductivity.

Gap symmetry of superconducting borocarbide YNi2B2C and skutterudite PrOs4Sb12

“…Indeed all four states have the same quasiparticle density of states as d-wave superconductors [16]. As we shall see later, however, the multigap model is incompatible with the angle dependent magnetothermal conductivity observed by Izawa et al [5] and the universal heat conduction in κ zz observed by Suzuki et al [17] in Sr 2 RuO 4 . On the other hand these thermal con-ductivity data are fully consistent with f-wave sc shown in Fig.…”

“…The associated magnetothermal conductivity provides a unique window to investigate nodal structures of ∆(k) . In this way Izawa et al have succeeded in identifying the gap symmetry of Sr 2 RuO 4 , CeCoIn 5 and κ-(ET) 2 Cu(NCS) 2 [5,6,7]. More recently the magnetothermal conductivity data from YNi 2 B 2 C and PrOs 4 Sb 12 has revealed the presence of point nodes in ∆(k) [8,11].…”

“…As is readily seen the φ-dependence of the thermal conductivity is adequate to identify one of four ∆(k) gap functions we have considered sofar. In this way ∆(k) in Sr 2 RuO 4 [5], CeCoIn 5 [6] and κ-(ET) 2 Cu(NCS) 2 [7] are identified. On the other hand the φ-dependence of κ xx and κ xy in YBCO so far determined [30,32,33] do not match the one for d x 2 −y 2 -wave.…”

“…Indeed Izawa et al have shown f-wave sc in Sr 2 RuO 4 [5], d-wave sc in CeCoIn 5 [6] and κ-(ET) 2 Cu(NCS) 2 [7] through the angle dependent magnetothermal conductivity. More recently gap functions ∆(k) in borocarbide YNi 2 B 2 C and skutterudite PrOs 4 Sb 12 are shown to have point nodes and described in terms of s+g-wave sc [8][9][10][11][12].…”

Coherence peak in the spin susceptibility from nesting in spin-triplet superconductors: A probe for line nodes inSr2RuO4

“…The absence of the angle dependence of the thermal conductivity within the a-b plane 10,11 shows that the line nodes run horizontally on the Fermi surface. The angle resolved ultrasound attenuation experiment 7 is compatible with the horizontal line nodes.…”