Measurement of 2DEG Transport on a Thin Film of Superfluid Liquid Helium

Transport measurements of electrons on the surface of liquid helium are usually done via capacitive coupling from underlying electrodes. In order to investigate high-density and quantum many-body phenomena, such as the quantum melting of Wigner crystals, thin (<10 nm) films of helium are necessary [1]. Atomically smooth amorphous metals have enabled indirect transport measurements of electrons atop thin helium films, employed in measurements using a biased strip of amorphous metal over which electrons moved. However, direct capacitive control of electrons in this thin helium film regime has been experimentally challenging and unexplored due to potential barriers from gaps between electrodes impeding transport. Here, we report electron transport with an architecture using thin superconducting gates with a thin layer of highly resistive and smooth amorphous metal deposited over them, creating a gapless transport device with capacitive control of the electrons above a thin helium film.

[1] K. E. Castoria and S. A. Lyon, J. Low Temp. Phys. 210, 441(2023).