Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 24: Unconventional Superconductors
TT 24.5: Talk
Wednesday, March 19, 2025, 10:45–11:00, H31
Complex impedance scanning tunneling microscopy as a probe for unconventional superconductors — •Amber Mozes1, Sanghun Lee2, Tjerk Benschop1, Koen Bastiaans1, and Milan Allan1,2 — 1Leiden University, Leiden, The Netherlands — 2LMU, Munich, Germany
In many unconventional superconductors, the superconducting state is spatially inhomogeneous, and macroscopic superconductivity is suppressed. To understand what causes this suppression of superconductivity, we are developing a probe to measure the local complex impedance. We combine scanning tunneling microscopy (STM) with microwave microscopy. This could, in principle, allow to locally probe the impedance response and relate this to inhomogeneity in free carrier density whenever macroscopic homogeneity is suppressed. More specifically, it would be possible to measure the kinetic inductance of a superconductor, governed by the Meissner effect, as well as local resistivity from non superconducting carriers. Implementation of complex impedance measurements in STM requires a microwave impedance matching circuit to enable simultaneous DC and AC readout of the tip-sample response. I will present our recently developed chip circuits that are in situ replaceable, enabling sample specific circuit design, with the aim to impedance match for superconducting sample properties.
Keywords: Scanning tunneling microscopy; Microwave; Unconventional superconductivity; Complex impedance