Resistivity and magnetoresistivity near the metal-insulator and superconductor-insulator transition in granular Al-Ge
Granular Al-Ge films, just on the metallic side of the critical volume fraction φc (50.7% Al), are found to have critical fields in excess of 1.5T at 0.47 K due to the fine granular nature of the Al. In barely insulating films where φc − φ < 2.2% (φ is the volume fraction of aluminum), Josephson junction coupling dominates the behaviour below Tc. For 3.4% ⩽ (φ − φ) ⩽ 6.2%, the resistivity diverges strongly below Tc and a large negative magnetoresistivity (MR) is observed. This behaviour is explained in terms of quasiparticle tunnelling or alternatively by the Adkins charging model. The high negative MR is explained using a magnetic field-dependent superconducting energy gap. The normal resistivity in the insulating films obeys the hopping relation ρ = ρ0 exp(T0/T)x above Tc and also below Tc in a field of 3.45 T, which quenches all superconductivity in the Al below Tc = 1.61 K.
Year of publication: |
1994
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Authors: | Eytan, G. ; Zaken, E. ; Rosenbaum, R. ; McLachlan, D.S. ; Albers, A. |
Published in: |
Physica A: Statistical Mechanics and its Applications. - Elsevier, ISSN 0378-4371. - Vol. 207.1994, 1, p. 240-244
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Publisher: |
Elsevier |
Saved in:
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