Conductivity measurement of helium surface electrons in the coexistence of adsorbed 2D atomic hydrogen gas

Cold hydrogen atoms (H) are adsorbed on liquid helium surface to form two-dimensional (2D) quantum gas. Because of the boson nature of H atoms, when 2D H gas is cold and dense enough, it is expected to exhibit a transition to superfluid phase by Kosterlitz-Thouless mechanism. In order to sense the state of 2D H gas, we used helium surface electrons as a probe. Since the conductivity of surface electrons is sensitively influenced by collisions with its environment, such as He vapor atoms and ripplons, it is expected to detect the existence of H atoms on the same surface. We prepared a 2D mixture gas of H and electrons on a helium surface and measured the conductivity of the electrons. Strong magnetic field was applied to avoid chemical processes: electron attachment on H atom and H-H recombination. We employed pulse excited edge-magnetoplasmon (EMP) technique for the conductivity measurement. We show EMP spectrum under the influence of H atoms and discuss the potentiality of surface electrons for probing states of adsorbed 2D H gas.