Cryogenic amplifier with high sensitivity and stability for noise-STM

Local shot noise spectroscopy with scanning tunneling microscopy (STM) has proven to be a powerful technique to investigate the electronic properties of quantum materials. It provides direct and non-invasive insight into the tunneling charge quanta or dynamics at the atomic scale. Due to the typically weak noise signal and the presence of low frequency spurious noise, local noise experiments require a high-resolution measurement amplifier. Here, we present a newly developed high-resolution noise amplifier that we implemented in three different STMs. Compared to our previous generation, we obtain more than a 20-fold improvement in the noise resolution, allowing us to resolve values of the effective charge as small as 0.01e. Our amplifier opens new possibilities for studying electronic properties in novel materials such as d-wave superconductors. In addition to this, it can give direct information about the local electron temperature in STM experiments.