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arXiv · 1902.05843

Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes

F. Levy-Bertrand·T. Klein·T. Grenet·O. Dupré·A. Benoît·A. Bideaud·O. Bourrion·M. Calvo·A. Catalano·A. Gomez·J. Goupy·L. Grünhaupt·U. v. Luepke·N. Maleeva·F. Valenti·I. M. Pop·A. Monfardini
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Abstract

We report on a detailed study of the optical response and $T_c-\rho$ phase diagram ($T_c$ being the superconducting critical temperature and $\rho$ the normal state resistivity of the film) of granular aluminum, combining transport measurements and a high resolution optical spectroscopy technique. The $T_c-\rho$ phase diagram is discussed as resulting from an interplay between the phase stiffness, the Coulomb repulsion and the superconducting gap $\Delta$. We provide a direct evidence for two different types of well resolved sub-gap absorptions, at $\omega_1\simeq\Delta$ and at $\Delta\lesssim\omega_2\lesssim2\Delta$ (decreasing with increasing resistivity).

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F. Levy-Bertrand, T. Klein, T. Grenet, O. Dupré, A. Benoît, A. Bideaud, O. Bourrion, M. Calvo, A. Catalano, A. Gomez, J. Goupy, L. Grünhaupt, U. v. Luepke, N. Maleeva, F. Valenti, I. M. Pop, A. Monfardini. 2019-02-15. Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes. https://doi.org/10.1103/physrevb.99.094506

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