Physics Research Seminar: Ingmar Swart (Utrecht University, Netherlands)
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Welcome to join us for a research seminar by Ingmar Swart from Utrecht University, Netherlands!
Prof. Swart leads a research group studying quantum matter using scanning probe techniques.
Host: Peter Liljeroth/Atomic Scale Physics Group
Title: Local noise measurements – and what you can learn from them
Abstract:
Experimental measurements are subject to noise, which can have different origins. In most cases, noise on experimental signals, such as the tunnel current in an STM, is considered a nuisance and one aims to minimize it. However, some noise sources contain useful information. For example, the thermal excitation of charge carriers in a material leads to electronic noise which can be used to measure temperature. Another well-known noise source is shot-noise, caused by the discrete nature of electron charge. Shot-noise measurements have been used to reveal the effective charge of carriers in mesoscopic systems, ranging from Cooper pairs in superconductors to quasiparticles with fractional charge in 2D interacting electron gases subject to high magnetic fields (fractional quantum Hall effect).
In this talk, I will present a new generation high-frequency amplifier that enables local shot-noise measurements in a scanning tunneling microscope. The amplifier, developed in collaboration with the group of Milan Allan (Leiden/LMU Munich), operates at T = 1.2K, and tolerates perpendicular magnetic fields up to B = 8T. I will demonstrate the performance of the amplifier and show results obtained on two different superconductors.