Thermal conductivity of superconducting alloy films in a perpendicular magnetic field

Abstract

We have measured the thermal conductivity of superconducting films of indium-bismuth alloys in a perpendicular magnetic field. The films were condensed onto glass substrates held at 77 K, and had thicknesses ranging from 1050 to 4570 A. Values of the ratio of the BCS coherence length to the electron mean free path for these films were 9. We made measurements at temperatures T between 0.3 and 1.0 K for magnetic fields ranging from zero to above the upper. critical field H". We plotted the thermal conductivity as a function of magnetic field. The resulting curve, except for some rounding very close to H, 2, was found to be approximately linear for magnetic fields greater than 60% of H". This linear behavior is in qualitative agreement with the theory of Caroli and Cyrot for the electronic part of the thermal conductivity of a dirty superconductor near H". This theory predicts that the ratio of the slope of the thermal-conductivity curve to the slope of the magnetization curve at H" is a universal function of the reduced temperature t = T/T"where T, is the zero-field transition temperature. We infer the magnetization of our films with the help of theoretical calculations which are based on the critical-field values. The experimental values of the ratio of the slopes are 10 -30% below the theoretical values. In attempting to explain this discrepancy, we speculate that v, varies more rapidly as a function of temperature than theory predicts. The same conclusion has been drawn previously from both similar and different types of experiments.

Full superconducting gap in the doped topological crystalline insulator Sn0.6In0.4Te

“…Therefore, there is no residual linear term of κ 0 /T , as seen in Nb and InBi. 27,28 In contrast, a finite κ 0 /T in zero field is usually observed in a superconductor with nodal gap, if the heat current is not perpendicular to the nodal directions. 20 For example, κ 0 /T = 1.41 mW K −2 cm −1 was observed with heat current in the ab plane for the overdoped cuprate Tl 2 Ba 2 CuO 6+δ (Tl-2201), a d-wave superconductor with T c = 15 K. 29 However, if the heat current is perpendicular to the nodal directions, the κ 0 /T will still be zero despite the existence of gap nodes.…”

Fully gapped superconducting state in Au 2 Pb: A natural candidate for topological superconductor

“…For a clean s-wave superconductor with a single gap, κ 0 (H)/T should grow exponentially with field, as observed in Nb [33]. While for s-wave InBi in the dirty limit, the curve is exponential at low H, crossing over to a roughly linear behavior closer to H c2 [34]. In the case of NbSe 2 , the distinct κ 0 (H)/T behavior was well explained by multiple superconducting gaps with different magnitudes [37].…”

“…For nodeless superconductors, there are no fermionic quasiparticles to conduct heat as T → 0, since all electrons become Cooper pairs. Therefore, there is no residual linear term κ 0 /T , as seen in conventional s-wave superconductors Nb and InBi [33,34]. However, for unconventional superconductors with nodes in the superconducting gap, the nodal quasiparticles will contribute a substantial κ 0 /T in zero field.…”

“…4. For comparison, the data of the clean s-wave superconductor Nb [33], the dirty s-wave superconducting alloy InBi [34], the multiband s-wave superconductor [33], the dirty s-wave superconducting alloy InBi [34], the multiband s-wave superconductor NbSe2 [37], and an overdoped d-wave cuprate superconductor Tl-2201 [35].…”

Bulk Evidence for Single-Gaps-Wave Superconductivity in the Intercalated Graphite SuperconductorC6Yb

“…6 Yb plotted as a function of H=H c2 , with the small contribution from graphite impurities subtracted off. For comparison we also display low-temperature data for the clean s-wave superconductor Nb [24], the dirty s-wave superconducting alloy InBi [26], the multigap superconductor MgB 2 [28], and an overdoped sample of the d-wave superconductor Tl-2201 [19].…”