| Andreev reflection at the boundary between one-dimensional weakly interacting electron gas and a superconductor is analyzed within the poor man's scaling approach in the basis of scattering states. Extending the method of Matveev, Yue and Glazman [Phys. Rev. Lett. 71, 3351 (1993)] we derive the renormalization group equations for the energy-dependent scattering matrix of the normal-metal/superconductor interface. We show that the initial high-energy cutoff in the renormalization procedure is set up by the superconducting energy gap Δ provided the superconducting coherence length exceeds the range of interaction potential in the electron gas. Our results describe a suppression of the differential Andreev conductance at low bias voltages V< Vc, where the ratio Vc/Δ is a power-law function of the normal-state interface resistance. The theory can explain a strong dependence of the zero bias Andreev conductance on the gate voltage observed in experiments with carbon-nanotube/superconductor junctions by Morpurgo et al. [Science 286, 263 (2001)]. |
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