Session A1 - Microwave-Induced Resistance Oscillation in 2-D Electron Systems.
INVITED session, Monday morning, March 22
517A, Palais des Congres
Simple irradiation in the GHz range on 2D electron systems has been shown to have remarkable consequences on the transport at low magnetic fields. It was found by Zudov, et. al.(M.A. Zudov, R.R. Du, J.A. Simmons, J.L. Reno, Phys. Rev. B. 64, 201311 (2001).) that radiation from 30 to 120GHz imposed on a high quality heterostructure resulted in a series of magnetoresistance oscillations periodic in amp;#61472;the radiation frequency/cyclotron frequency, using bare GaAs electron mass. Subsequently it was observed by Mani, et al(R.G. Mani, J.H. Smet, K. von Klitzing, V. Narayanamurty, W.B. Johnson, V. Umansky, cond-mat/0303034; Nature 420, 646 (2002).) and Zudov, et al(M.A. Zudov, R.R. Du, L.N. Pfeiffer, K.W. West, cond-mat/0210034; Phys. Rev. Lett. 90, 046807 (2003).) that in high mobility samples the minima can form apparent zeroes, with the temperature dependence activated. Addressing this same issue, we report experimental results of low temperature magnetotransport in high mobility 2D electron systems exposed to radiation up to 20GHz frequency using a simple dipole configuration. Magnetoresistance oscillations are observed as in the previously reported results using higher frequency radiation on 2D systems, however minima here can be seen to extend to negative biases. Also, zeroes previously reported are not observed persistently around the full sample perimeters. In addition, under radiation, voltages are observed from internal to external contacts in the absence of applied driving currents and are apparently not due to simple rectification. These voltages, generated in the absence of applied driving currents, correspond in amplitude and B-field position to the original radiation induced oscillations, and can demonstrate dependence upon B-field sweep direction. Overall these findings are consistent with micro- and macroscopic theoretical pictures of radiation induced transport and current instabilities due to local negative resistivities.(A.C. Durst, S. Sachdev, N. Read, S.M. Girvin, cond-mat/0301569; Phys. Rev. Lett. 91, 086803 (2003).), (A.V. Andreev, I.L. Aleiner, A. J. Millis, cond-mat/0302063; Phys. Rev. Lett. 91, 056803 (2003)). However, an important property of the radiation-induced minima is the temperature dependence: the previous experimental work\footnote[2]R.G. Mani, J.H. Smet, K. von Klitzing, V. Narayanamurty, W.B. Johnson, V. Umansky, cond-mat/0303034; Nature 420, 646 (2002). \footnote[3]M.A. Zudov, R.R. Du, L.N. Pfeiffer, K.W. West, cond-mat/0210034; Phys. Rev. Lett. 90, 046807 (2003). showed activated transport consistent with an energy gap in the transport spectrum. We examined the transport minima and found a complicated temperature dependence outside of present theoretical understanding. The temperature development is not necessarily activated over a large temperature range, with hysteresis possible in the minima. In addition, we find all temperature development is severely dependent upon the incident radiation power.
collaborators L.N. Pfeiffer, K.W. West, Bell Laboratories, Lucent Technologies