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TT: Fachverband Tiefe Temperaturen
TT 42: Superconductivity: Tunneling and Josephson Junctions
TT 42.9: Vortrag
Donnerstag, 20. März 2025, 11:45–12:00, H32
Superconducting Atomic Contacts under Microwave Irradiation, Photon-Assisted Tunneling and Fractional Shapiro Steps — •Oliver Irtenkauf1, Patrick Raif1,2, Carlos Cuevas1,3, and Elke Scheer1 — 1University of Konstanz, Germany — 2University of Basel, Switzerland — 3Universidad Autónoma de Madrid, Spain
We form an atomic contact from a mechanically controlled aluminum break junction and irradiate it with microwaves in its superconducting state [1]. In the dI/dV spectra, we observe the well-known structures caused by photon-assisted tunneling, which, in the case of tunnel contacts, are fully explained by the Tien-Gordon (TG) model [2]. However, for higher-order transport processes, the model requires extensions, as shown in simulations based on the TG model [3,4]. Shapiro steps, i.e., replicas of the supercurrent, reveal deviations from the theoretical predictions described in references [5,6]. Fractional Shapiro steps, which we observe in atomic contacts with high-transmission channels at high frequencies, differ from traditional Shapiro steps and represent a new phenomenon.
[1] P. Raif, Master Thesis, Uni. Konstanz (2024);
[2] P. K. Tien & J. P. Gordon, PR 129, 647 (1963);
[3] P. E. Gregers-Hansen et al., PRL 31, 524 (1973);
[4] J.C. Cuevas et al., PRL 88, 157001 (2002);
[5] G. Falci, V. Bubanja & G. Schön, Z. Phys. 85, 451 (1991);
[6] P. Kot et al., PRB 101, 134507 (2020).
Keywords: Superconductivity; Atomic Contact; Microwave Irradiation; Shapiro Steps; Photo-Assisted Tunneling