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
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.
PACS: 63.20.Kr – Phonon-electron and phonon-phonon interactions / 74.20.Mn – Polarons and bipolarons / 74.20.Fg – BCS theoy and its development
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2004