Hysteresis and spikes in the quantum Hall effect

Abstract

We observe sharp peaks and strong hysteresis in the electronic transport of a two-dimensional electron gas (2DEG) in the region of the integral quantum Hall effect. The peaks decay on time scales ranging from several minutes to more than an hour. Momentary grounding of some of the contacts can vastly modify the strength of the peaks. All these features disappear under application of a negative bias voltage to the backside of the specimen. We conclude, that a conduction channel parallel to the high mobility 2DEG is the origin for the peaks and their hysteretic behavior.The hallmark of the integral and fractional quantum Hall effects are wide regions of vanishing magnetoresistance and wide plateaus in Hall resistance [1][2][3]. These features are centered around magnetic fields, that correspond to integral or fractional fillings of Landau levels of a two-dimensional electron gas (2DEG). Their origin is quantization of the electron orbits into Landau levels and the formation of localized states in real, slightly disordered 2DEG in the presence of a high magnetic field, B. Electrons in the localized states provide a reservoir, which is in equilibrium with the current-carrying, delocalized states and keep their occupation constant over wide stretches of B. While in the integral quantum Hall effect (IQHE) [1] the ingredients of this picture are of single-particle origin, they are of many-particle origin in the fractional quantum Hall effect (FQHE) [2,3].Two recent experiments have observed hysteretic behavior and/or peak formation in electronic transport of 2DEG in the regime of the FQHE [4,5]. Minor discrepancies in data taken on opposite field sweeps are common and are usually attributed to the large inductance of the magnet and the resulting time delays or to slight temperature differences between both sweeps. However, the recently observed effects are very large. Kronmueller et al. [4] observed the appearance of a huge spike at the position of the ν = 2/3 minimum when the magnetic field is ramped very slowly. The time scale for development of this feature can be as long as hours, which suggested the involvement of nuclear spins in its creation. Cho et al.[5] have observed hysteretic behavior in resistance traces taken on several fractions around filling factor ν = 1/2 and attribute it to non-equilibrium phases of composite fermions in this regime. The origin of these observations remains puzzling and the nature of the underlying nonequilibria remains unclear.We have observed strong hysteresis and the formation of sharp peaks in magneto-transport experiments on 2DEGs in quantum wells in the regime of the IQHE at temperatures of ∼0.1K. To our recollection, we have never observed such features in a traditional single heterojunction interface sample. The characteristic decay times for the sharp peaks can be as long as several hours. Their life time can be strongly altered by momentary grounding of the contacts. Hysteresis and spikes disappear on application of a voltage bias to an electrode on the back side of the s...

Realization of an Interacting Two-Valley AlAs Bilayer System

“…Also, keeping the Fermi energies of the layers equal as a function of sweeping magnetic field requires some charge transfer between the wells. There are, therefore, possibly interesting phenomena at high magnetic fields that can be explored in this system [22]. Third, the system has some remarkable properties even at zero or small magnetic fields.…”

Charge metastability and hysteresis in the quantum Hall regime

“…These hysteretic effects have been associated with a number of physical phenomena, including non-equilibrium charge distributions [3][4][5] , long-lived eddy currents [6][7][8][9] within the interior of the 2DES, first order phase transitions involving the electron spin [10][11][12][13][14][15] or pseudospin [16][17][18][19] degrees of freedom, and metastable orientations of the electron nematic phases at high Landau level occupancy 20 . In the majority of these experiments the behavior of the collective electron state was inferred from measurements of magnetoresistance, which was found to depend strongly on the sweep rate and direction of the magnetic field.…”

Layer-charge instability in unbalanced bilayer systems in the quantum Hall regime

“…Zhu et al [13] reported hysteresis in 2D electron systems with a parallel conducting layer. In their case, the parallel layer was a parasitic, low-mobility, doping layer at a distance of 75 to 95 nm away from the high-mobility 2D electrons.…”