Influence of a parallel magnetic field on microwave-induced zero-resistance states and magnetoplasmon resonance

In an ultra-clean two-dimensional electron system (2DES), we have observed the magnetoplasmon resonance (MPR) through its microwave-photoconductivity, concurrently with the microwave-induced resistance oscillations (MIRO) and zero-resistance states (ZRS). It is found that the MIRO/ZRS is strongly suppressed by a moderate magnetic field (<1T) parallel to the 2DES, while the MPR is robust against a parallel magnetic field. These findings have not been addressed by current models proposed to explain the MIRO/ZRS.