Effects of phonon interaction on pairing in high-Tc superconductors

Yunkyu Bang

doi:10.1103/PhysRevB.78.075116

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Effects of phonon interaction on pairing in high-Tc superconductors

Yunkyu Bang

DOI 10.1103/PhysRevB.78.075116 · Physical Review B

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Abstract

We study the effects of phonon interaction on the superconducting pairing in the background of a d-wave gap, mediated by antiferromagnetic (AFM) spin fluctuations, using coupled BCS gap equations. We found that phonon interaction can induce a s-wave component to the d-wave gap in the (D+S) form with an interaction anisotropy and in the (D+iS) form without anisotropy, respectively. In either case, however, Tc is not enhanced compared to the pure d-wave pairing without phonon interaction. On the other hand, anisotropic phonon interaction can dramatically enhance the d-wave pairing itself and therefore Tc, together with the AFM spin fluctuation interaction. This (DAFM+Dph) type pairing exhibits strongly reduced isotope coefficient despite the large enhancement of Tc by phonon interaction. Finally, we study the combined type of (DAFM+Dph+iS) gap and calculate the penetration depth and specific heat to be compared with the experiments.