Radiation-induced magnetoresistance oscillations in two-dimensional electron systems under bichromatic irradiation

Abstract

We analyze the magnetoresistance Rxx oscillations in high-mobility two-dimensional electron systems induced by the combined driving of two radiation fields of frequency ω1 and ω2, based on the balance-equation approach to magnetotransport for high-carrier-density systems in Faraday geometry. It is shown that under bichromatic irradiation of ω2 ∼ 1.5ω1, most of the characterstic peak-valley pairs in the curve of Rxx versus magnetic field in the case of monochromatic irradiation of either ω1 or ω2 disappear, except the one around ω1/ωc ∼ 2 or ω2/ωc ∼ 3. Rxx oscillations show up mainly as new peak-valley structures around other positions related to multiple photon processes of mixing frequencies ω1 + ω2, ω2 − ω1, etc. Many minima of these resistance peak-valley pairs can descend down to negative with enhancing radiation strength, indicating the possible bichromatic zero-resistance states.

Phase-sensitive magnetoresistance oscillations induced by commensurate bichromatic irradiations in a two-dimensional electron system

“…In the previous investigations, we dealt with bichromatic radiations having incommensurate frequencies, 32 i.e., frequencies x 1 and x 2 are so different that for arbitrary nonzero integers m 1 and m 2 , jm 1 x 1 þ m 2 x 2 j are always much larger than 1/s 0 , where s 0 stands for the scale of time variation of the dc, or slowly varying, detecting field E 0 , or the time scale within which one carries out the transport measurement, whichever the shorter. In the incommensurate case, the second term in Eq.…”

“…10 These bichromatic radiation experiments also disclosed the importance of multiple photon processes with mixing frequencies under intense radiations. 15,16,32 The investigations of bichromatic radiation, however, were limited to the incommensurate case, i.e., the difference of two frequencies x 1 and x 2 , jm 1 x 1 þ m 2 x 2 j (for arbitrary nonzero integers m 1 and m 2 ), is much larger than 1/s 0 , where s 0 stands for the time scale carrying out the transport measurement. 32 Recently, Shi et al 44 pointed out that if the frequencies of two radiation fields are commensurate, there may exist a nonzero phase-related contribution to the oscillating magnetoresistance induced by circularly polarized radiations.…”