Séminaire nano-électronique quantique

Fabian Natterer (University of Zurich)
Sparse-Sampling, Multifrequency Excitation and High Dynamic Range Tunneling Spectroscopy
le mardi 1er juillet 2025 à 14:00
Lieu : Salle Rémy Lemaire K223, Institut Néel

Personne à contacter : Alexandre Assouline ()

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. After examining the key concepts of QPI, parallel spectroscopy, and compressive sensing, 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.