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TT: Fachverband Tiefe Temperaturen

TT 16: Poster Session Superconductivity, Cryogenic Particle Detectors, Cryotechnique

TT 16.3: Poster

Montag, 16. März 2020, 15:00–19:00, P2/EG

Scanning tunneling spectroscopy on disordered superconductors — •Martina Trahms¹, Idan Tamir¹, Franzisca Gorniaczyk², Marc Westig¹, Karl Jacobs³, Dan Shahar², and Katharina J. Franke¹ — ¹Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany. — ²Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot 7610001, Israel. — ³I. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany.

In some materials superconductivity co-exists with a certain amount of disorder. The true microscopic nature of disordered superconductors remains unknown [1]. These systems have mainly been investigated in transport experiments which average over the macroscopic sample area. More recently, scanning tunneling microscopy/spectroscopy (STM/STS) measurements revealed large spatial fluctuations of the superconducting gap, indicating a local modification of the ground-state [2]. Here, we will present preliminary results of high resolution STM measurements enabled by utilizing superconducting tips. We study thin films of amorphous InO and polycrystalline NbN as well as a 400 nm TiN sample. We observe local gap variations on the nanometer length scale and resolve a number of in-gap states showing high fluctuations both in energy and spatial distribution.

[1] P. W. Anderson, J. Phys. Chem. Solids 11, 26-30 (1959).

[2] B. Sacépé et al., Phys. Rev. Lett. 101, 157006 (2008).