Theory of point-contact spectroscopy in electron-doped cuprate superconductors

In the hole-doped d x2 - y2 -wave cuprate superconductors, due to the midgap surface state (MSS), a zero-bias conductance peak (ZBCP) is widely observed in [110] interface point-contact spectroscopy (PCS). However, a ZBCP of this geometry is rarely observed in the electron-doped cuprates, even though their pairing symmetry is still likely of the d x2 - y2 wave type. We argue that this is due to the coexistence of antiferromagnetic (AF) and superconducting orders. Generalizing the Blonder-Tinkham-Klapwijk formula to include an AF coupling, it is shown explicitly that the MSS is destroyed by the AF order. The calculated PCS is in good agreement with the experiments.