Local tunneling characteristics near a grain boundary of a d-wave superconductor as probed by a normal-metal or a low-Tc-superconductor STM tip

摘要

We studied the local single-particle tunneling characteristics [as observed with scanningtunnel microscopy (STM)] for N D and S D tunneling, where N is a normalmetal, S is a s-wave superconductor, and D is a d-wave superconductor witha {100} | {110} grain boundary. The tunneling Hamiltonian method was used. Theself-consistent order parameter is first determined using the quasiclassical Green'sfunctionmethod, and then the tunneling characteristics at various distances fromthe interface, reectivity of the interface, and temperature are studied. For N Dtunneling, a zero-bias conductance peak (ZBCP) occurs near the interface with diminishingmagnitude away from it. For S D tunneling, the ZBCP splits to exhibitthe gap of the s-wave low-Tc superconducting tunneling tip and there is a range ofnegative conductance just outside the peaks when the tunneling point is near thegrain boundary. The results are compared with those obtained by using a constantorder parameter in each grain.