A phenomenological model that considers different secondary $id_{ xy}$ gap amplitudes and quasiparticle effective charges for each nodal direction, is proposed to explain the observed anisotropic node removal by a magnetic field in high-$T_{ c}$ cuprates. Two independent parity-breaking condensates $<\bar{ \Psi_{ i}}\bigwedge{ \Psi}_{ i}>$ develop, implying the induction of a magnetic moment per each nodal direction. The model outcomes are in agreement with the experimentally found relation $\Delta_{ i}\sim\sqrt{ B}$. The secondary gap vanishes through a second-order phase transition at a critical temperature whose value for underdoped nodal-oriented YBCO is estimated to be $\sim 6K$ for a field of 15 T.
Categories: cond-mat.supr-con hep-ph