Effect of orthorhombicity on the superconducting phase of the cuprates: a Monte Carlo study

Abstract

Using a semi-classical Monte Carlo simulation technique, the reduced BCS pairing projection of the t– t′– J model is used to investigate properties of its superconducting phase. We report on the symmetry and magnitude of the energy gap parameter at low temperatures, and its dependence on filling for a range of different ratios of t to t′, corresponding to different band structures. Both extended s-wave and d-wave superconducting order are found. D-wave ordering is shown to be strongly dependent on Van Hove singularities in the band structure. Orthorhombic distortion, which splits the degeneracy of Van Hove singularities, is shown to result in a corresponding split of the peak of the d-wave energy gap parameter as a function of filling. This distortion is also shown to enhance the extended s-wave ordering, giving it a definite phase relation to the d-wave component. The form, relative strength, and doping dependence of the simulated superconducting phases are in good qualitative agreement with experimentally determined superconducting phase diagrams.