2001/03/31 by Kunihiko Yamaji · 33 citations
Materials Science · Physics and Astronomy · #Boron and Carbon Nanomaterials Research #Cooper pair #Coulomb #Instability #Physics of Superconductivity and Magnetism #Polarization (electrochemistry) #Scattering #Superconductivity #Superconductivity in MgB2 and Alloys #Wave vector #cond-mat.supr-con
paper · pdf · doi:10.1143/jpsj.70.1476
published in Journal of the Physical Society of Japan 70(6), 1476-1479 (Physical Society of Japan) · 4 pages, to be published in J. Phys. Soc. Jpn. vol. 70, No. 6
arxiv created 2001/04/27 · openalex publication_date 2001/06/15 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Using the tight-binding method for the π-bands in MgB2, the Hubbard on-site Coulomb interaction on two inequivalent boron pz-orbitals is transformed into expressions in terms of π-band operators. For scattering processes relevant to the problemin which a wave vector \bf q is parallel to z, it is found to take a relatively simple form consisting of intra-band Coulomb scattering, interband pair scattering etc. with large constant coupling constants. This allows to get a simple expression for the amplitude of interband pair scattering between two π-bands, which diverges if the interband polarization function in it becomes large enough.The latter was approximately evaluated and found to be largely enhanced in the band structure in MgB2. These results lead to a divergent interband pair scattering, meaning two-band-type superconducting instability with enhanced Tc. Adding a subsidiary BCS attractive interaction in each band into consideration, a semi-quantitative gap equation is given, and Tc and isotope exponent α are derived. The present instability is asserted to be the origin of high Tc in MgB2.