Publication Date:
2017-09-16
Description:
Author(s): Uwe S. Pracht, Tommaso Cea, Nimrod Bachar, Guy Deutscher, Eli Farber, Martin Dressel, Marc Scheffler, Claudio Castellani, Antonio M. García-García, and Lara Benfatto In ordinary superconductors the two collective modes of the complex order parameter are usually strongly resilient to the spectroscopic observation. The amplitude or Higgs mode is weakly coupled to the electromagnetic field and it overlaps with the continuum of single-particle excitations at 2 Δ , which buries its signal. The phase or Goldstone mode is optically inert, and it is boosted to the plasma frequency by Coulomb interactions. In the present work, terahertz experiments and theoretical calculations are combined in order to demonstrate the existence of an alternative route for the optical visibility of the Goldstone mode in a nanostructured granular Al thin film. The Coulomb screening due to the grains self-capacitance and the intrinsic inhomogeneity of the local superfluid stiffness due to shell effects lead to finite-frequency subgap absorption of the phase modes, showing that nanograins arrays are a promising setting to control the Goldstone mode via optical means. [Phys. Rev. B 96, 094514] Published Fri Sep 15, 2017
Keywords:
Superfluidity and superconductivity
Print ISSN:
1098-0121
Electronic ISSN:
1095-3795
Topics:
Physics
