B-periodic oscillations in microwave irradiated high-mobility 2D electron gas

Recently a new type of B-periodic magneto-oscillations was observed [1] in the Hall bar samples of a 2D electron gas under the irradiation of microwaves (MW, frequency $\omega )$. The period $\Delta B$ is determined by $\omega $, the electron density$ n_{s}$, and the distance between potential probes $L$, $\Delta B\propto n_s /\omega L$. The phenomenon is explained by coherent excitation of edge magnetoplasmons in the region near the contacts. Using very high-mobility (8- 20 $\times $ 10$^{6}$ cm$^{2}$/Vs) GaAs/Al$_{x}$Ga$_{1-x}$As heterostructures, we were able to observe both the MW-induced resistance oscillations, which is 1/B -periodic, and the B-periodic oscillations in the same sample, in the frequency range 27 to 130 GHz. Experimental data as well as a brief discussion will be presented. [1] Kukushkin et al, Phys. Rev. Lett. 92, 236803 (2004).