Recent experiments [1,2] have shown that under relatively weak dc electric fields and in the regime of separated Landau leveles (LLs), 2Γ/ħωc < εdc < 1, the differential resistivity of a high-mobility 2DES is dramatically reduced. The characteristic electrostatic energy was found to be closely related to the LL width, Γ, and the observed reduction of resistance was explained employing the “displacement” model, i.e. dc-induced suppression of both intra-Landau and inter-LL scattering off of impurities. This observation resembles microwave-induced suppression of resistance by low frequency microwaves 2Γ/ħ < ω < ωc which was explained in terms of intra-LL absorption [3-5]. Similar dc-induced suppression of resistance was also reported by another experiment [2] where it was associated with the “inelastic” mechanism, i.e. dc-induced non-equilibrium corrections to the distribution function leading to spectral diffusion of electrons. Since in the regime of weak electric fields “inelastic” and “displacement” mechanisms have comparable contributions [6], the exact origin of the observed suppression remains unsettled awaiting further experimental and theoretical studies. In particular, for quantitative comparison of theory and experiment it is very desirable to extend the theoretical treatment into the regime of separated LLs and lower temperatures T < ħωc.
More recent experiments [7,8] revealed that under certain conditions the differential resistance can drop all the way to zero forming new dc-induced zero-differential resistance states (ZdRS). In one experiment [7] ZdRS was observed at T < 2 K and relatively high magnetic fields B > 6 kG, where SdHO are well developed. In fact, ZdRS emerged from the SdHO maxima when a dc current passed through a 2DES exceeded some critical value, I > 10 μA. The transition to ZdRS was accompanied by a reproducible negative spike and temporal fluctuations. In another experiment [8] ZdRS was also observed at T < 2 K but the magnetic field was considerably weaker, 1.5 < B < 3.0 kG and ZdRS did not rely on the SdHO maxima. Here, ZdRS appeared when I1 < I < I2, where I1 ≈ 8 μA and I2 ≈ 25 μA, where I1 was found to be roughly B-independent as long as LLs are separated. In contrast with Ref. [7] neither overshoot to negative values nor temporal fluctuations were detected. Therefore, it remains to be seen if dc-induced ZdRS observed in these experiments have the same origin. It is also worthwhile to investigate if ZdRS occur due to instability with respect to negative-differential resistance state leading to formation of current domains, in analogy with microwave-induced ZRS. Since the experimental setup does not require microwave radiation, searching for such dc-induced current domains should be significantly easier to implement.
[1] W. Zhang, H. S. Chiang, M. A. Zudov, L. N. Pfeiffer, and K. W. West, “Magnetotransport in a two-dimensional electron system in dc electric fields”, Physical Review B 75, 041304 (2007) [abstract] [full text]
[2] J. Zhang, S. Vitkalov, A. A. Bykov, A. K. Kalagin, and A. K. Bakarov, “Effect of a dc electric field on the longitudinal resistance of two-dimensional electrons in a magnetic field”, Physical Review B 75, 081305 (2007) [abstract] [full text]
[3] R. L. Willett, L. N. Pfeiffer, and K. W. West, “Evidence for Current-Flow Anomalies in the Irradiated 2D Electron System at Small Magnetic Fields”, Physical Review Letters 93, 026804 (2004)[abstract] [full text]
[4] S. I. Dorozhkin, J. H. Smet, V. Umansky, and K. von Klitzing, “Microwave photoresponse in the two-dimensional electron system caused by intra-Landau-level transitions”, Physical Review B 71, 201306 (2005) [abstract] [full text]
[5] M. A. Zudov, R. R. Du, L. N. Pfeiffer, and K. W. West, “Bichromatic Microwave Photoresistance of a Two-Dimensional Electron System”, Physical Review Letters 96, 236804 (2006) [abstract] [full text]
[6] M. G. Vavilov, I. L. Aleiner, and L. I. Glazman, “Non-linear Resistivity of a Two-Dimensional Electron Gas in a Magnetic Field”, Physical Review B 76, 115331 (2006) [abstract] [full text]
[7] A. A. Bykov, J.-Q. Zhang, S. Vitkalov, A. K. Kalagin, and A. K. Bakarov, “Zero differential resistance state of two dimensional electron systems in strong magnetic fields”, Physical Review Letters 99, 116801 (2007) [abstract] [full text]
[8] W. Zhang, M. A. Zudov, L. N. Pfeiffer and K. W. West, “Resonant Phonon Scattering in Quantum Hall Systems Driven by dc Electric Fields”, Physical Review Letters 100, 036805 (2008) [abstract] [full text]