Doppler shift of the Andreev bound states at the YBCO surface

The effect of applied magnetic field on the zero-bias conductance peak (ZBC P) observed in tunneling spectra of YBCO reveals the number of states is co nserved; the splitting magnitude depends upon field orientation and hystere sis. Both the conservation and anisotropy are consistent with the ZBCP resu lting from quasiparticle (QP) Andreev bound states at the YBCO surface with a Doppler shift arising from the scalar product between the QP velocity an d superfluid momentum, v(F) . P-S. The hysteresis is consistent with the ef fects of strong vortex pinning on the surface screening currents.