Field induced $d_{x^2-y^2}+id_{xy}$ state and marginal stability of high-Tc superconductors

摘要

It is shown that the {\em complex} $d_{xy}$ component is generated in d-wavesuperconductor in the magnetic field. As one enters superconducting state atfinite field the normal to superconducting transition occurs into bulk$d_{x^2-y^2}+i d_{xy}$ state . The driving force for the transition is thelinear coupling between magnetic field and non zero magnetization of the$d_{x^2-y^2}+i d_{xy}$ condensate. The external magnetic field violates parityand time reversal symmetries and the nodal quasiparticle states respond bygenerating the $id_{xy}$ component of the order parameter, with the magnitudeestimated to be on the order of few Kelvin. Parity (P) and time reversal (T)symmetries are violated in this state.