Magnetic-field-induced id(xy) order in d(x(2)-y(2)) superconductor

The interaction between planar quasiparticles in a d(x2-y2) superconductor and quantized vortices associated with a magnetic field perpendicular to th e plane is shown to induce a pair potential with d(xy) symmetry, out of pha se with the d(x2-y2) order. A microscopic calculation of a. process involvi ng quasiparticle scattering by the supercurrent around a vortex and Andreev reflection from its core is presented. Other processes that also lead to a n id,, pair potential are discussed. It is argued that such a fully gapped state may be the high-field low-temperature phase observed by Krishana and Ong ct al, in magnetothermal conductivity measurements of superconducting s ingle-crystal Bi-2212. (C) 1998 Published by Elsevier Science Ltd. All righ ts reserved.