Zero resistance is a rare occurrence in condensed matter physics, usually signaling a novel state of matter. Until recently, the observation of zero-resistance was unique to superconductivity and the quantized Hall effects. Recent experiments on microwave-irradiated ultra-high mobility 2DES (μ > 107 cm2/V s) brought a big surprise to the scientific community - microwave-induced zero-resistance states (ZRS) [1,2]. Emerging from the MIRO minima, ZRS extend over a wide interval of magnetic field, occurring when the microwave frequency somewhat exceeds an integer multiple of the cyclotron frequency of the 2DES:
where the width of ZRS, 2Δ, can span magnetic field ranges corresponding to several tens in filling factors, depending on Pω, T, and 2DES quality. More recently ZRS associated with fractional values of εac, e.g. εac = 3/2,1/2,2/3 [3], and ZRS appearing only under the bichromatic microwave irradiation [4] were reported. Unlike the quantum Hall effect, vanishing of diagonal resistance in microwave-irradiated 2DES is not accompanied by Hall plateaus which remain classical. Shortly after the discovery of ZRS, zero-conductance states were observed in Corbino rings [5], confirming the applicability of the standard dc magnetotransport tensor relation and ruling out a few theoretical proposals.
The disappearance of resistance appeared to be the most intriguing aspect in microwave-irradiated 2DES and was promptly addressed by a very powerful macroscopic argument [6], explaining ZRS in terms of the inability of the system to sustain negative resistance. Based on Maxwell equations, this argument, leads to a conclusion that, regardless of the microscopic origin of the underlying negative resistance, the 2DES is unstable with respect to formation of intricate current patterns - current domains. These domains are characterized by a unique magnitude of the local current density at which the resistance is not negative, but zero. Under common boundary conditions, domain orientation and size yield zero potential drop responsible for the observation of ZRS in macroscopic samples. Very recently it was theoretically suggested that the domains are not necessarily static but instead might evolve in time [7]. Experimental verification of the domain model remains a subject of future studies. While recent experiments with bichromatic microwaves provided indirect support for negative resistance, there exists no direct experimental evidence for the domain structure.
[1] R. G. Mani, J. H. Smet, K. von Klitzing, V. Narayanamurti, W. B. Johnson, and V. Umanskyk, “Zero-resistance states induced by electromagnetic-wave excitation in GaAs/AlGaAs heterostructures”, Nature 420, 646 (2002)[link]
[2] M. A. Zudov, R. R. Du, L. N. Pfeiffer, and K. W. West, “Evidence for a New Dissipationless Effect in 2D Electronic Transport”, Physical Review Letters 90, 046807 (2003) [abstract] [full text]
[3] M. A. Zudov, R. R. Du, L. N. Pfeiffer, and K. W. West, “Multiphoton processes in microwave photoresistance of two-dimensional electron systems”, Physical Review B 73, 041303 (2006) [abstract] [full text]
[4] 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]
[5] C. L. Yang, M. A. Zudov, T. A. Knuuttila, R. R. Du, L. N. Pfeiffer, and K. W. West, “Observation of Microwave-Induced Zero-Conductance State in Corbino Rings of a Two-Dimensional Electron System”, Physical Review Letters 91, 096803 (2003) [abstract] [full text]
[6] A. V. Andreev, I. L. Aleiner, and A. J. Millis, “Dynamical Symmetry Breaking as the Origin of the Zero-dc-Resistance State in an ac-Driven System”, Physical Review Letters 91, 056803 (2003) [abstract] [full text]
[7] I. G. Finkler and B. I. Halperin, “Microwave-induced zero-resistance states are not necessarily static”, Physical Review B 79, 085315 (2009) [abstract] [full text]