Theory of the Superconductivity of MgB_2 (Condensed Matter and Statistical Physics)

概要

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We consider MgB_2 to be a structure-dependent superconductor, the B_2 plane of the MgB_2 crystal to be superconducting and the Mg plane to be a tunneling junction plane between the B_2 planes. We set up the superconducting .interaction within the B_2 plane between two adjacent planes and the coupling pair interactions in the perpendicular direction of the B_2 plane. Using the mean field approximation for the equation of motion of the superconducting electron, we solve the Green function of the electron and obtain the order parameters Δ_‖ (T) and Δ_⊥(T) of the intra B_2 plane and inter B_2 plane electrons, respectively. It is found that these two order parameters have the same T_c with an appropriate choice of model parameters. Our gap function in the form Δ_‖ + const × Δ_⊥ cosq, where q represents the momentum along the c-axis direction, leads to a two-peak structure in the density of states, which explains the experimental measurement of "two gaps" in MgB_2. The bulk properties of the specific heat, the NMR and the thermal conductivity are also calculated.
理論物理学刊行会の論文
2004-05-25