Thermal properties and electronic structure of superconducting germanide skutterudites and : a multi-band perspective

Abstract

We present the temperature (T) and magnetic field (H) dependence of heat capacity (C) of the superconducting skutterudite compounds and along with their electronic band structure. We show that the zero-field C(T) in the superconducting state of both the samples cannot be explained using an isotropic single gap or an anisotropic single gap perspective. We find that it can only be explained in terms of two superconducting gaps. The Sommerfeld coefficient of electronic heat capacity in the mixed superconducting state of these compounds obtained from the C(T) closely follows the measured C(H) at 2 K. Observation of two distinct linear regions in with a change of slope in between for both the samples supports the fact that the two gap superconductivity is intrinsic to this family of skutterudites. A large observed in the limit of zero magnetic field for both the samples indicates the possibility of anisotropy in the superconducting gaps of these compounds. Apart from supporting the evidence for the above experimental observations, the band structure calculations also show that the anisotropy of the gaps in is different from that of .

Keywords:

• Skutterudites
• multi-gap superconductivity
• heat capacity

Acknowledgements

We thank R. K. Meena for sample preparation and Parul Arora for heat capacity measurements.

Notes

No potential conflict of interest was reported by the authors.

1 In the case of paramagnetic impurities, the term z in the Schottky contribution to heat capacity is given by and . Here, n is the number of paramagnetic centres, g is the Lande’s g-factor, is the Bohr’s magneton, is the Boltzmann constant, and are the applied and internal fields, respectively.