Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 16: Scanning Probe Techniques: Method Development

O 16.2: Talk

Monday, March 17, 2025, 15:15–15:30, H25

Multifrequency Excitation and High Dynamic Range Tunneling Spectroscopy — Philipp E.J. Maier, Ajla Karić, Carolina A. Marques, Berk Zengin, and •Fabian D. Natterer — Department of Physics, University of Zurich, Winterthurerstrasse 190, CH-8057, Switzerland

The massive number of spectra required for high-resolution quasiparticle interference of low-dimensional quantum materials motivates the development of faster point spectroscopies. While the advent of parallel spectroscopy and compressive sensing enhancements has provided welcome speed boosts, these come at a cost. The application of a sinusoidal voltage on the nonlinearities in the current-voltage characteristics of a tunneling junction generates a frequency comb of higher order current-harmonics. While their parallel measurement enables faster tunneling spectroscopy, it unfortunately averages longest where the currents are largest, leading to poor signal-to-noise ratios for smaller signals associated with features close to the Fermi level. Here, we introduce a multifrequency excitation mode that increases the averaging time for small currents, enabling fast and high-resolution spectroscopy. Additionally, the AC excitation of our method can be used to dramatically increase the dynamical current range by exactly and deliberately suppressing the large amplitude, low order harmonics that would otherwise saturate the preamplifier stage.

Keywords: Scanning tunneling microscopy; Scanning tunneling spectroscopy; quasiparticle interference; dynamic range; multifrequency excitation