Eur. Phys. J. B 41, 197-200 (2004)
https://doi.org/10.1140/epjb/e2004-00309-4

Polaron cross-overs and d-wave superconductivity in Hubbard-Holstein model

Condensed Matter Physics Group, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta-700064, India

Corresponding author: ^a ramakumar@cmp.saha.ernet.in

Received: 27 May 2004
Revised: 9 July 2004
Published online: 12 October 2004

Abstract

We present a theoretical study of superconductivity of polarons in the Hubbard-Holstein model. A residual kinematic interaction proportional to the square of the polaron hopping energy between polarons and phonons provides a pairing field for the polarons. We find that superconducting instability in the d-wave channel is possible with small transition temperatures which is maximum in the large to small polaron cross-over region. An s-wave instability is found to be not possible when the effective on-site interaction between polarons is repulsive.