Giant Fano factor and bistability in a Corbino disk in the quantum Hall effect breakdown regime

Abstract

We performed noise measurements for a Corbino disk in the quantum Hall effect breakdown regime. We investigated two Corbino-disk-type devices with different sizes and observed that the Fano factor increases when the length between the contacts doubles. This observation is consistent with the avalanche picture suggested by the bootstrap electron heating model. The temperature dependence of the Fano factor indicates that the avalanche effect becomes more prominent as temperature decreases. Moreover, in the highly nonlinear regime, negative differential resistance and temporal oscillation due to bistability are found. A possible interpretation of this result is that Zener tunneling of electrons between Landau levels occurs.

Gyrotropic Zener tunneling and nonlinear IV curves in the zero-energy Landau level of graphene in a strong magnetic field

“…Our 9 T result at ν = 0, E c = 100 kV/m, is by a factor of four larger than the quoted result in GaAs heterostructures. On the basis of inelastic electron - acoustic phonon scattering, the BSEH model leads to E c ∝ B 3/2 , which has been verified experimentally 28 , but even in these experiments E c extrapolates only to 14 kV/m at 9 T. Taking also into account the weak coupling to acoustic phonons in similar graphene samples 29 , we conclude that in graphene we are not dealing with thermal runaway at the onset of the nonlinear IV characteristics. Further evidence of nonthermal origin of the IV characteristics is provided by the absence of hysteresis, which one would expect to exist for this type of instabilities.…”

Bulk dissipation in the quantum anomalous Hall effect

“…Upon tuning V g (Fig. 2b), we observed further reduction in I AC and a wide range of gate voltage (−14 V ≤ V g ≤ −4.5 V), over which I AC < 1 pA, indicating that the QAH state was well-formed [28]. Further investigation demonstrated that heating of the sample and excursions in gate voltage away from this plateau led to partial demagnetization (Section IV of supplement).…”

“…In the Corbino geometry, no edges connect the source and drain contacts, eliminating edge contributions from conduction measured with transport. While insensitive to the Hall voltage, transport in Corbino devices is an intensive measurement of the bulk conductivity σ xx , which is invaluable when studying dissipation in systems exhibiting topological edge transport [28][29][30][31].…”

Dirac fermion optics and plasmonics in graphene microwave devices

“…Apart from the aforementioned Hall bars, constrictions and antidot arrays, another interesting geometry for the investigation of the QHBD is the Corbino disk, where the QHE manifests itself in the absence of edge currents and an insulating bulk, leading to a suppression of the source-drain current, see fig. 5.7b and c. In GaAs/AlGaAs 2DEGs of this geometry, the QHBD was investigated in conjunction with noise measurements in the 0 − 200 kHz range [281,285]. They observe super-Poissonian Fano factors at the breakdown and justify this within the framework of the avalanche mechanism in BSEH.…”

“…To overcome 1/f noise at these high source-drain currents, the noise power spectral density is measured in a 1 GHz bandwidth window around 5 GHz, which requires the sample to be embedded in a two-terminal co-planar waveguide, contrarily to most other studies, where the sample geometry is either a Hall bar or a Corbino disk. In short, we are combining the homogeneous constrictions introduced by Bliek et al [276] with noise measurements similar to those carried out by the Kobayashi group [281,285,297] and an intrinsic BLG sample from Yang et al [145] to shed a new light on the old problem of the quantum Hall breakdown.…”