Theory of Zero-Resistance States Generated by Radiation in GaAs/AlGaAs (original) (raw)

Zero-resistance states induced by electromagnetic-wave excitation in GaAs/AlGaAs heterostructures

Nature, 2002

The observation of vanishing electrical resistance in condensed matter has led to the discovery of new phenomena such as, for example, superconductivity, where a zero-resistance state can be detected in a metal below a transition temperature Tc (ref. 1). More recently, quantum Hall effects were discovered from investigations of zero-resistance states at low temperatures and high magnetic fields in two-dimensional electron systems (2DESs). In quantum Hall systems and superconductors, zero-resistance states often coincide with the appearance of a gap in the energy spectrum. Here we report the observation of zero-resistance states and energy gaps in a surprising setting: ultrahigh-mobility GaAs/AlGaAs heterostructures that contain a 2DES exhibit vanishing diagonal resistance without Hall resistance quantization at low temperatures and low magnetic fields when the specimen is subjected to electromagnetic wave excitation. Zero-resistance-states occur about magnetic fields B = 4/5 Bf and B = 4/9Bf, where Bf = 2πfm*/e</ ITALIC>,m* is the electron mass, e is the electron charge, and f is the electromagnetic-wave frequency. Activated transport measurements on the resistance minima also indicate an energy gap at the Fermi level. The results suggest an unexpected radiation-induced, electronic-state-transition in the GaAs/AlGaAs 2DES.

Zero-resistance states induced by electromagnetic waves in a 2DEG

2004

We report the experimental detection of novel zero-resistance states induced by electromagnetic wave excitation in ultra high mobility GaAs/AlGaAs heterostructure devices, at low magnetic fields, B, in the large filling factor limit. Vanishing resistance is observed in the vicinity of B = [4/(4j+1)] B_f, where Bf =2π f m^*/e, where m^* an the effective mass, e is the charge, and f is the microwave frequency. The dependence of the effect is reported as a function of f, the temperature, the power, the current, and other experimental variables.[1] [1] R. G. Mani, J. H. Smet, K. von Klitzing, V. Narayanamurti, W. B. Johnson, and V. Umansky, Nature 420, 646 (2002); cond-mat/0303034, 0305507, 0306388, 0310474, 0311010.