Affiliation: Department of Physics, Yonsei University

Research Field: Transition metal dichalcogenides, Topological insulators, Unconventional superconductors, High frequency measurements

Scanning noise spectroscopy

Scanning tunneling spectroscopy has become indispensable for investigating the local electronic structure of correlated electron systems. However, valuable information about the dynamics in electric charge transport cannot be accessed by conventional time-averaged spectroscopy techniques. An example is the granularity of charge that leads to current fluctuations; so called shot noise. Correlations can lead to deviations from Poissonian noise which are smeared out in the averaged current value. In mesoscopic systems, noise-spectroscopy measurements have been widely used to study the dynamics of strongly correlated phenomena. Here, we present a newly developed noise spectroscopy technique, for which we combine a Scanning Tunneling Microscope (STM) with a novel MHz amplifier to bring noise-spectroscopy measurements to the atomic scale. We demonstrate the Poissonian tunneling process on a Au(111) surface and the Andreev reflection induced multiple charge tunneling in a Josephson junction. In addition, we observe unexpected non-Poissonian tunneling process on a cuprate high temperature uperconductor with atomic resolution. This provides us a new way to unveil electronic properties hidden in the time-averaged transport measurements on exotic quantum materials