Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 2: Scanning probe techniques: Method development I
O 2.3: Talk
Monday, March 12, 2018, 11:00–11:15, MA 004
Influence of microwave radiation on an STM Josephson junction — •Olof Peters1, Nils Bogdanoff1, Gaël Reecht1, Clemens B. Winkelmann2, and Katharina J. Franke1 — 1Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Univ. Grenoble Alpes, Institut Neél, 25 Avenue des Martyrs, 38042 Grenoble, France
Besides its applications in quantum mechanical circuits the Josephson effect is a powerful tool to study the superconducting ground state. The combination of a Josephson junction with the atomic-scale precision of a scanning tunnelling microscope (STM) would enable the measurement of the superconducting order parameter around single magnetic defects. We present here a current-biased Josephson junction in an STM at T=1.3 K. Both tip and sample consist of Pb.
Extending the setup with coaxial cables suitable for microwaves makes it possible to couple radiation up to f=26 GHz into the junction where the tip acts as an antenna. The Josephson current responds to the incident microwave radiation by showing multiple steps, with the step position and width depending on the amplitude and the frequency of the microwave radiation. Simulations of the step spacing reveal, that the current is dominated by Cooper pair tunnelling. The power dependence of the steps suggests that the Cooper pair tunnelling is a photon-assisted incoherent process similar as seen by [1].
[1] A. Roychowdhury et al., Phys. Rev. Applied 4, 034011 (2015)