Prog. Theor. Phys. Vol. 111 No. 5 (2004) pp. 707-719
Theory of the Superconductivity of MgB2
14-8-5, Sugano, Ichikawa 272-0824, Japan
2Department of Physics, Faculty of Science and Technology,
Tokyo University of Science, Noda 278-8510, Japan
(Received December 8, 2003)
We consider MgB2 to be a structure-dependent superconductor, the
B2 plane of the MgB2 crystal to be superconducting and the
Mg plane to be a tunneling junction plane between the B2
planes. We set up the superconducting interaction within the B2
plane between two adjacent planes and the coupling pair interactions
in the perpendicular direction of the B2 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 B2
plane and inter B2 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⊥ cos
q, 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 MgB2. The bulk properties of the
specific heat, the NMR and the thermal conductivity
are also calculated.
DOI : 10.1143/PTP.111.707
J. Nagamatsu, N. Nakagawa, T. Muranaka, Y. Zentani and J. Akimitsu, Nature 410 (2001), 63[CrossRef].
- P. B. Allen, “Phonons and Superconductive Transition Temperature" in Dynamical Properties of Solids, ed. G. K. Horton and A. A. Maradudin (North Holland Co., Amsterdam, 1980).
I. I. Mazin and V. P. Antrop, Physica C 385 (2003), 49[CrossRef].
H. T. Choi, M. L. Cohen and S. G. Louie, Physica C 385 (2003), 66[CrossRef].
- P. C. Canfield and G. W. Crabtree, Phys. Today 56 (2003), 34.
S. Souma, Y. Machida, T. Sato, T. Takahashi, H. Matsui, S.-C. Wang, H. Ding, A. Kaminski, J. C. Campuzano, S. Sasaki and K. Kadowaki, Nature 423 (2003), 65[CrossRef].
M. Iavarone, G. Karapetrov, A. E. Koshelev, W. K. Kwok, G. W. Crabtree, D. G. Hinks, W. N. Kang, Eun-Mi Choi, Hyun Jung Kim, Hyeong-Jin Kim and S. I. Lee, Phys. Rev. Lett. 89 (2002), 187002[APS].
- T. Soda and Y. Wada, Prog. Theor. Phys. 36 (1966), 1111[PTP].
F. Bouquet, R. A. Fisher, N. E. Phillips, D. G. Hinks and J. D. Jorgensen, Phys. Rev. Lett. 87 (2001), 047001[APS].
- G. Rickayzen, “The Theory of Bardeen, Cooper, and Schrieffer" in Superconductivity, vol. 1, ed. R. D. Parks (M. Dekker Inc., New York, 1967), p. 110.
L. P. Kadanoff and P. C. Martin, Phys. Rev. 124 (1961), 670[APS].
Citing Article(s) :
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