Magnetic field- and frequency-dependence- of the phase-shift in the linearly-polarized microwave radiation-induced magnetoresistance oscillations in the GaAs/AlGaAs system

Nonequilibrium transport studies of the radiation-induced magnetoresistance oscillations (RIMOs) have revealed striking photo-excited zero-resistance states in the GaAs/AlGaAs two-dimensional electron system [1]. Further observations show that RIMOs are linear-polarization-angle-sensitive and follow a sinusoidal fitting formula, R$_{\mathrm{xx}}(\theta )=$A $\pm$ Ccos$^{2}(\theta $-$\theta_{0})$ where R$_{\mathrm{xx}}$ is the diagonal resistance, $\theta $ is the polarization angle, and $\theta_{0}$ is the extracted phase shift. At the present, $\theta_{0}$ is known to be magnetic- and frequency dependent [2]. Here, we perform magnetic mappings at small $\theta $ intervals, at a number of radiation frequencies, to study the variation of the phase shift with the magnetic field and frequency. The relationship between phase shift and magnetic fields/frequency will be critically examined and reported in this presentation. \\[4pt] [1] R. G. Mani \textit{et al.}, Phys. Rev. B 84, 085308 (2011). \\[0pt] [2] A. N. Ramanayaka \textit{et al.}, Phys. Rev. B 85, 205315 (2012).