The AC Hall effect for electrons on liquid helium in ultra-high magnetic fields

Current-voltage phase shift measurements are reported between electrodes situated near the rim of an array located below a charged liquid helium surface. Data are taken in magnetic fields up to 20 T at a temperature near 2 K. Under these conditions, the ultra-quantum limit is reached, where the Landau level width is larger than the electron thermal energy. Interpreting the data in terms of the AC Hall effect, or edge magnetoplasmon, suggests that the Hall resistivity deviates from its classical value for fields greater than 10 T.