Field-induced dx2-y2+ idxy state and marginal stability of high-Tc superconductors

It is shown that the complex d(xy) component is generated in a d-wave superconductor in the magnetic field. As one enters a superconducting state at the finite field the normal to superconducting transition occurs into the bulk d(x2-y2) + id(xy) state. The driving force for the transition is the linear coupling between the magnetic field and the nonzero magnetization of the d(x2)-(y2) + id(xy) condensate. The external magnetic field violates parity and time-reversal symmetries and the nodal quasiparticle states respond by generating the id(xy) component of the order parameter, with the magnitude estimated to be on the order of a few kelvin. Parity (P) and time-reversal (T) symmetries are violated in this state.