Vortex state of a d-wave superconductor in high-Tc cuprates.

Abstract

We study theoretically the vortex state of a d-wave superconductor in a magnetic field parallel to the c axis. We find, except in the immediate vicinity of the superconducting transition temperature, that a square lattice tilted by \ensuremath{\pi}/4 from the a axis gives the most stable configuration, which provides the simplest interpretation of a recent small angle neutron scattering experiment by Keimer et al. and a more recent scanning tunnel microscope experiment by Maggio-Aprile et al. The residual density of states is shown to follow a \ensuremath{\surd}B law in a wide field region consistent with an earlier prediction by Volovik. The effect of d-s mixture is also studied. The most important effect appears to be a suppression of the upper critical field at low temperatures by 5--10 %. \textcopyright{} 1996 The American Physical Society.