Acoustoelectric transport of electrons on helium

We report on the acoustoelectric transport of electrons on helium induced by coupling to piezoelectric surface acoustic waves (SAWs). In our device, the SAWs propagate along the surface of a lithium niobate piezoelectric crystal that is submerged beneath a thin layer of superfluid ⁴He. Electrons are deposited onto the superfluid and float ~10 nm above its surface. When SAWs propagate along the lithium niobate substrate, electrons are trapped in the moving electric potential of the SAW and transported across the device at the speed of the piezoacoustic wave. Electrodes positioned beneath the lithium niobate capacitively couple to the electrons and are used to detect acoustoelectric transport. We have performed time and frequency domain measurements and analysis to characterize the electric current dragged along by the SAW. To our knowledge, these measurements constitute the first demonstration of acoustoelectric charging pumping of electrons on helium.