Enhancing Tc within phonon mediated coexistence of s + d wave superconductivity in cuprates

Abstract

The high superconducting transition temperatures T c of oxide cuprates and their proximity to an antiferromagnetic ground state have frequently been attributed to unconventional pairing mechanisms and a d-wave superconducting order parameter. Even though effects due to the lattice have been observed experimentally, their role on superconductivity is mainly questioned. Here it will be shown that some features of hole doped superconducting cuprates can be well modeled by combining two order parameters of different symmetry, i.e. s + d, which interact through phonon induced interband scattering. A polaronic type phase (charge density wave like) precedes the superconducting state and signals the onset of the pseudogap state. Both effects, interband interactions and polaronic level shift are shown to substantially enhance T c.