THz spectroscopy of superconducting ultrathin films

Author

Dressel, Martin ; Pracht, Uwe S. ; Heintze, Eric ; Scheffler, Marc ; Gorshunov, Boris ; Sherman, Daniel ; Frydman, Aviad ; Ilin, Konstantin S. ; Henrich, Dagmar ; Siegel, Mel

Author_Institution

Phys. Inst., Univ. Stuttgart, Stuttgart, Germany

fYear

2014

fDate

14-19 Sept. 2014

Firstpage

1

Lastpage

2

Abstract

Coherent-source THz spectroscopy was employed to measure the charge carrier dynamics and excitations of ultrathin superconducting films at low temperatures. While the properties of weakly disordered superconductors can be well described by the BCS theory, significant deviations are observed as disorder increases towards the superconductor-insulator transition. A comparative study including tunneling and optical spectroscopy reveals the importance of Coulomb interactions on the energy gap of disordered superconductors. We also discuss the possibility of collective low-frequency excitations due to the Higgs mode, which become long-lived and well defined in the vicinity of a quantum critical point.

Keywords

niobium; niobium compounds; optical conductivity; superconducting energy gap; superconducting thin films; superconducting transitions; superconductive tunnelling; tantalum compounds; terahertz wave spectra; titanium compounds; type II superconductors; BCS theory; Coulomb interactions; Higgs mode; Nb; NbN; TaN; TiN; charge carrier dynamics; coherent-source THz spectroscopy; collective low-frequency excitations; energy gap; optical spectroscopy; quantum critical point; superconducting ultrathin films; superconductor-insulator transition; tunneling; weakly disordered superconductors; Films; Granular superconductors; Insulators; Spectroscopy; Superconducting films; Temperature measurement;

fLanguage

English

Publisher

ieee

Conference_Titel

Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2014 39th International Conference on

Conference_Location

Tucson, AZ

Type

conf

DOI

10.1109/IRMMW-THz.2014.6956417

Filename

6956417