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arXiv · 1901.02814

Optical conductivity of granular aluminum films near the Mott metal-to-insulator transition

Aviv Glezer Moshe·Eli Farber·Guy Deutscher
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Abstract

We report measurements of the energy gap of granular aluminum films by THz spectroscopy. We find that as the grains progressively decouple, the coupling ratio $2Δ(0)/k_{B}T_{c}$ increases above the BCS weak coupling ratio $3.53$, and reaches values consistent with an approach to BCS-BEC crossover for the high resistivity samples, expected from the short coherence length. The Mattis-Bardeen theory describes remarkably well the behavior of $σ_{1,s}/σ_{1,n}$ for all samples up to very high normal state resistivities.

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Aviv Glezer Moshe, Eli Farber, Guy Deutscher. 2019-06-04. Optical conductivity of granular aluminum films near the Mott metal-to-insulator transition. https://doi.org/10.1103/physrevb.99.224503

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