Hysteretic phenomena in a 2DEG in the quantum Hall effect regime, studied in a transport experiment

Abstract

We investigated experimentally non-equilibrium state of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime, studying the hysteresis of magnetoresistance of a 2DEG with a constriction. The large amplitude of the hysteresis enabled us to make the consistent phenomenological description of the hysteresis. We studied the dependence on the magnetic field sweep prehistory (minor loop measurements), recovered the anhysteretic curve, and studied the time dependence of the magnetoresistance. We showed that the hysteresis of magnetoresistance of a 2DEG in the QHE regime has significant phenomenological similarities with the hysteresis of magnetization of ferromagnetic materials, showing multistability, jumps of relaxation, and having the anhysteretic curve. Nevertheless, we revealed the crucial difference, manifested itself in an unusual inverted (anti-coercive) behavior of the magnetoresistance hysteresis. The time relaxation of the hysteresis has fast and slow regimes, similar to that of non-equilibrium magnetization of a 2DEG in QHE regime pointing to their common origin. We studied the dependence of the hysteresis loop area on the lithographic width of the constriction and found the threshold value of width ∼1.35 µm beyond which the hysteresis is not observed. This points to the edge nature of the non-equilibrium currents (NECs) and allows us to determine the width of the NECs area (∼0.5 µm). We suggest the qualitative picture of the observed hysteresis, based on non-equilibrium redistribution of the electrons among the Landau level states and assuming huge imbalance between the population of bulk and edge electronic states.

Nonequilibrium phenomena in bilayer electron systems

“…These observations are often interpreted as a manifestation of the breaking of interlayer equilibrium by a magnetic field sweep. Although wide (tens of µm) single-layer Hall bars are usually free from magnetoresistance hysteresis, it can appear in submicron-wide single-layer constrictions of a 2DEG [10,11]. This hysteresis can be explained by the absence of equilibrium between the edge and the bulk.…”

Suspended semiconductor nanostructures: physics and technology

“…Despite more than 40 years of intensive research, some transport phenomena associated with the quantum Hall effect (QHE) [166] still attract considerable attention. They include, for example, 3D QHE [167], hysteresis phenomena [168,169] and the QHE in fundamentally new systems such as graphene [170,171] or topological insulators [172,173]. Unusual phenomena in the QHE regime are also observed in suspended semiconductor structures with a 2DEG.…”