Unusual effects of anisotropy on the specific heat of ceramic and single crystal MgB2

Abstract

The two-gap structure in the superconducting state of MgB 2 gives rise to unusual thermodynamic properties which depart markedly from the isotropic single-band BCS model, both in their temperature-and field dependence. We report and discuss measurements of the specific heat up to 16 T on ceramic, and up to 14 T on single crystal samples, which demonstrate these effects in the bulk. The behavior in zero field is described in terms of two characteristic temperatures, a crossover temperature ≅ π , c

Vortex motion and flux-flow resistivity in dirty multiband superconductors

“…Scanning tunnel microscopy shows absence of zero-bias anomaly inside vortex cores which is typical for dirty superconductors 33 . Impurities at high concentration can be introduced in MgB 2 on demand during the preparation process producing nontrivial magnetic properties which have been intensively studied recently 28,[34][35][36][37] . The structure of this paper is as follows.…”

Advances in point-contact spectroscopy: two-band superconductor MgB2 (Review)

“…On the another hand, the energy gap of the π band goes to zero at the same T c as in the bulk, and correspondingly 2∆ π (0)/kT c = 1.4, which is much less than the value predicted by the weak coupling BCS theory. One can think of the π band as having intrinsically much lower T c ≈ 10 K than the bulk [22], and at higher temperatures its superconductivity is induced by a proximity effect in k-space from σ band [23]. This proximity effect is very peculiar.…”

The theory of thermodynamic and magnetic properties of multi-band superconductors

“…The main physical properties and the singularities are as follows (see for example, [53] and [54]) :…”