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VOLUME 64 (1996) | ISSUE 10 |
PAGE 713
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Pair tunneling in the low temperature conductivity of the Cd-Sb alloy high-resistance state neai the superconductor-insulator transition
Gantmakher V.F., Zverev V.N., Dolgopolov V.T., Shashkin A.A.
We have studied the temperature dependence, down to 30 mK, of the magnetoresistance of Cd-Sb alloy in the insulating phase that was obtained by annealing the quenched metallic superconducting (Tc И4.5К) phase of the alloy. Despite the sample in this state is superconducting no more, the observed negative magnetoresistance points to single-particle tunneling in the presence of the superconducting gap in the spectrum. At magnetic fields В < 2 Τ the ratio a(T, B) R(T, B)/R(T, В 4 Τ) has been found to be maximum at a temperature of about 0.1 K. This behavior indicates a change of the conductivity mechanism from single-particle tunneling to incoherent two-particle tunneling as the temperature decreases. PACS: 71.30.+h, 72.20.Pr, 74.50,+r
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