Shot noise in a normal-metal– d -wave superconductor junction with a {110} -oriented interface

The current fluctuations in a normal-metal--${d}_{{x}_{a}^{2}\ensuremath{-}{x}_{b}^{2}}$-wave superconductor junction with a ${110}$-oriented interface are investigated based on the scattering formalism. Our study exhibits an important consequence of the sign change of the d-wave order parameter. In the ballistic junction, the shot-noise power is finite within the maximum energy gap. In particular, in the tunneling limit, the noise-to-current ratio is zero at zero bias and quickly reaches the classical Schottky value $2e$ at a finite bias. If the tunneling barrier resides several coherence lengths away from the superconductor surface, more resonant-peak structures appear in the differential shot-noise power. The predicted current fluctuation behaviors are qualitatively different from those in a normal-metal--$s$-wave superconductor junction.