F. Bouquet

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 T c,π ≅13 K, and a critical temperature T c = T c,σ ≅38 K, whereas the mixed-state specific heat requires three characteristic fields, an isotropic crossover field μ 0 H c2,π ≅0.35 T, and an anisotropic upper critical field with extreme values μ 0 H c2,σ, c ≅3.5 T and μ 0 H c2,σ, ab ≅19 T, where the indexes π and σ refer to the three-dimensional and two-dimensional sheets of the Fermi surface. Irradiation-induced interband scattering tends to move the gaps toward a common value, and increases the upper critical field up to ∼28 T when T c ≅30 K.

Specific heat of Nb 3 Sn: The case for a second energy gap

We present specific-heat data for

Specific heat of MgB2 after irradiation

{\mathrm{Nb}}_{3}\mathrm{Sn}

Specific heat of MgB_2 after irradiation

, a well-known technically applied superconductor with a critical temperature

Modulated-bath ac calorimetry using modified commercial Peltier elements

{T}_{c}\ensuremath{\cong}18\phantom{\rule{0.3em}{0ex}}\mathrm{K}

Nonlinear excess conductivity of Bi2Sr2Can-1CunO2n+4+x (n=1,2) thin films

, in the temperature range from

Specific heat of ceramic and single crystal MgB2

1.2\phantom{\rule{0.5em}{0ex}}\text{to}\phantom{\rule{0.5em}{0ex}}200\phantom{\rule{0.3em}{0ex}}\mathrm{K}

Contribution of disorder to the hall effect in Bi2Sr2CuO6+δ

in zero magnetic field, and from

Specific heat of heavy-fermion CePd2Si2 in high magnetic fields

1.5\phantom{\rule{0.5em}{0ex}}\text{to}\phantom{\rule{0.5em}{0ex}}22\phantom{\rule{0.3em}{0ex}}\mathrm{K}

The vortex states of YBa2Cu3O7−δ: phase diagram; calorimetric and magnetic properties

in fields