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Andreev Reflection and Pair Breaking Effects at the Superconductor/Magnetic Semiconductor Interface

R. P. Panguluri·K. C. Ku·T. Wojtowicz·X. Liu·J. K. Furdyna·Y. B. Lyanda-Geller·N. Samarth·B. Nadgorny
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Abstract

We investigate the applicability of spin polarization measurements using Andreev reflection in a point contact geometry in heavily doped dilute magnetic semiconductors, such as (Ga,Mn)As. While we observe conventional Andreev reflection in non-magnetic (Ga,Be)As epilayers, our measurements indicate that in ferromagnetic (Ga,Mn)As epilayers with comparable hole concentration the conductance spectra can only be adequately described by a broadened density of states and a reduced superconducting gap. We suggest that these pair-breaking effects stem from inelastic scattering in the metallic impurity band of (Ga,Mn)As and can be explained by introducing a finite quasiparticle lifetime or a higher effective temperature. For (Ga,Mn)As with 8% Mn concentration and 140 K Curie temperature we evaluate the spin polarization to be 83+/-17%. PACS numbers: 72.25.Dc,72.25.Mk,74.45.+c

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R. P. Panguluri, K. C. Ku, T. Wojtowicz, X. Liu, J. K. Furdyna, Y. B. Lyanda-Geller, N. Samarth, B. Nadgorny. 2005-02-23. Andreev Reflection and Pair Breaking Effects at the Superconductor/Magnetic Semiconductor Interface. https://doi.org/10.1103/physrevb.72.054510

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