Heat capacity of mesoscopically disordered superconductors: implications for MgB2

Abstract

Electronic heat capacity C(T ) was calculated for a mesoscopically disordered s-wave superconductor treated as a spatial ensemble of domains with a continuously varying superconducting properties. The domains are assumed to have sizes L > ξ0, where ξ0 is the coherence length. Each domain is characterized by a certain critical temperature Tc0 in the range [0, Tc]. The averaging over the superconducting gap distribution leads to C(T ) ∼ T 2 for low T , whereas the specific heat anomaly at Tc is substantially smeared. The results explain well the C(T ) data for MgB2, where a multiplegap structure is observed.

Competition of Superconductivity and Charge Density Waves in Cuprates: Recent Evidence and Interpretation

“…In this connection, the failure of the most sophisticated approaches to make any prediction of true or, at least "bare" T c , (provided that the corresponding T c -value is not known a priori) despite hundreds of existing superconductors with varying fascinating properties, forced Phillips [63] to reject all apparently first-principle continuum theories in favor of his own percolative filamentary theory of superconductivity [64][65][66][67] (see also the random attractive Hubbard model studies of superconductivity [68,69] and the analysis of competition between superconductivity and charge density waves studied in the framework of similar scenarios [70][71][72]). We totally agree with such considerations in the sense of the important role of disorder in superconductors with high T c on the verge of crystal lattice instability [73][74][75][76][77][78][79][80][81][82][83]. Nevertheless, it is questionable whether a simple one-parameter "master function" of [63,67] would be able to make quantitative and practically precise predictions of T c .…”

“…Since, instead of one, two or more well-separated superconducting energy gaps, a continuous, sometimes wide, gap distribution is often observed (see results for Nb 3 Sn in [284] and MgB 2 in [285][286][287][288][289]), the original picture of the gap multiplicity in the momentum, k, space loses its beauty, whereas the competing scenario [76,290] of the spatial (r-space) extrinsic or intrinsic gap spread becomes more adequate and predictive [77][78][79]. For the case of cuprates, it has been recently shown experimentally that the spread is really spatial, but corresponds to the pseudogap (CDW gap) rather than its superconducting counterpart, the latter most probably being a single one [291] (see also the discussion in [83] and below).…”

Thermo-Magnetic Signature of a Superconducting Multi-band Square with Rough Surface

“…Huang et al [20] studied the effects of vacancy cluster defect in the entropy, enthalpy, free energy and heat capacity of silicon crystals, they found that the heat capacity decreases as the vacancy cluster defect size increased. Analytic calculation and a model that describes the low-temperature heat capacity of in-homogeneous cuprates compounds was performed in a mesoscopic disordered s-wave superconductor and the results reproduce the features of the heat capacity for MgB 2 [21][22][23]. Y. Kleeorin et al proposed a method to measure the entropy of mesoscopic systems via thermoelectric transport, they proved analytically and demonstrated numerically the applicability of their method [24].…”