Evidence of double-gap superconductivity in noncentrosymmetricNb0.18Re0.82single crystals

Abstract

Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. We combine point contact spectroscopy with specific heat measurements to probe the superconducting state in noncentrosymmetric Nb 0.18 Re 0.82 single crystals. The conductance spectra clearly exhibit a two-peak structure that is well reproduced within a two-band model with isotropic gaps in the spectrum. Such an observation is confirmed by distinct features of the specific heat both at low temperatures and in the range approaching the transition to the normal state. The analyses provide convincing evidence that the two-gap superconducting pairing is a robust feature of Nb 0.18 Re 0.82 .

Study of Nb0.18Re0.82non-centrosymmetric superconductor in the normal and superconducting states

“…The temperature dependence of the specific heat, C(T ), at different magnetic fields is shown in Fig. 4 (c 8.52 × 10 −6 mJ/mole-K 6 , which are consistent with the values obtained in the literature [18,19]. The γ value shows that the electronic correlations in the sample are not strong.…”

“…Hence, the mass enhancement is m e * = m e (1 + λ ep ) = 1.73 m e . The zero field C(T ) below T c is better explained in terms of a two-band model (see supplementary information), consistent with the single crystal study [19]. A power law behavior in C(T ) below T c would indicate a non s-wave behavior.…”

“…A power law behavior in C(T ) below T c would indicate a non s-wave behavior. However, we do not see power law behavior in our data (see Supplementary information), nevertheless to draw a conclusion about the symmetry of the gap from this measurement alone is rather tenuous and possibly other techniques, such as, magnetic resonance probes might be needed to determine the spin symmetry of the superconducting pairing unambiguously [19]. The quadratic dependence of ρ(T ) at low temperatures indicates the dominance of electronic correlations over electron-phonon scattering.…”

“…It is also observed that the MR does not follow the conventional metallic quadratic magnetic field dependence (MR ∝ H 2 ) [24]. As Nb 0.18 Re 0.82 is considered to be a multiband superconductor [19], we explore whether the magnetic field dependence follows the following expression for the MR in a simple two-band model [24].…”

Superconducting properties of the noncentrosymmetric superconductor TaOs

“…Re 24 Ti 5 [25], * rpsingh@iiserb.ac.in Nb 0. 18 Re 0.82 [26,27], and Re 6 Hf [28,29]. Most of these compounds exhibited single-band superconductivity except Nb 0.18 Re 0.82 , which showed double-gap superconductivity [27].…”