Y. Takane et K. Nakamura, INFLUENCE OF ELECTROMAGNETIC ENVIRONMENT ON TUNNELING CURRENT THROUGHNORMAL METAL-SUPERCONDUCTOR JUNCTIONS, Journal of the Physical Society of Japan, 64(12), 1995, pp. 4530-4534
Based on a tunneling Hamiltonian model, the two-electron tunneling cur
rent through normal metal-superconductor junctions is studied by incor
porating the influence of a dissipative electromagnetic environment wi
th an Ohmic resistor R. We show that at low bias voltages the two-elec
tron tunneling current displays a power-law behavior as I proportional
to V-4g+1, where g=e(2)R/pi h at zero temperature due to electromagne
tic fluctuations. This suggests that suppression of the two-electron t
unneling current is more remarkable compared with the usual tunneling
current in normal junctions where I proportional to V-g+1.