Microwave-induced magnetooscillations and absolute negative conductivity in a multisubband two-dimensional electron system on liquid helium

It is shown that nonequilibrium filling of an upper surface subband induced by a microwave resonance can be the origin of absolute negative conductivity and zero-resistance states for a two-dimensional electron system on liquid helium in a perpendicular magnetic field. Contrary to a similar effect reported for semiconductor systems, an oscillating sign-changing correction to the dc-magnetoconductivity shows up as a result of quasi-elastic inter-subband scattering that does not involve photons. This analysis explains the remarkable magnetooscillations and zero-resistance states recently observed in electron systems on liquid helium. c 2011 American Institute of Physics. [doi:10.1063/1.3552915]