Incoherent transport on the ν=2/3 quantum Hall edge

Abstract

The nature of edge state transport in quantum Hall systems has been studied intensely ever since Halperin [1] noted its importance for the quantization of the Hall conductance. Since then, there have been many developments in the study of edge states in the quantum Hall effect, including the prediction of multiple counterpropagating modes in the fractional quantum Hall regime, the prediction of edge mode renormalization due to disorder, and studies of how the sample confining potential affects the edge state structure (edge reconstruction), among others. In this paper, we study edge transport for the ν bulk = 2/3 edge in the disordered, fully incoherent transport regime. To do so, we use a hydrodynamic approximation for the calculation of voltage and temperature profiles along the edge of the sample. Within this formalism, we study two different bare mode structures with tunneling: the original edge structure predicted by Wen [2] and MacDonald [3], and the more complicated edge structure proposed by Meir [4], whose renormalization and transport characteristics were discussed by Wang, Meir and Gefen (WMG) [5]. We find that in the fully incoherent regime, the topological characteristics of transport (quantized electrical and heat conductance) are intact, with finite size corrections which are determined by the extent of equilibration. In particular, our calculation of conductance for the WMG model in a double QPC geometry reproduce conductance results of a recent experiment by Sabo et al. [21], which are inconsistent with the model of MacDonald. Our results can be explained in the charge/neutral mode picture, with incoherent analogues of the renormalization fixed points of Ref. [5]. Additionally, we find diffusive (∼ 1/L) conductivity corrections to the heat conductance in the fully incoherent regime for both models of the edge.

Topological Classification of Shot Noise on Fractional Quantum Hall Edges

“…Here T is the temperature, κ = π 2 k 2 B /(3h), and k B is Boltzmann's constant. It should be emphasized that, for edges with counterpropagating channels, the quantizations (1) and (2) holds under the condition (and is a hallmark) of the incoherent regime [6,7]. This regime is generic for nearly all FQHE experiments on such edges; reaching the coherent regime requires very low temperatures and/or very small distances between electrodes and/or special control over intermode tunneling [8].…”

Conductance plateaus and shot noise in fractional quantum Hall point contacts

“…Generally, γ depends on the edge structure and the intermode interactions. In particular, for two non-interacting channels with δν 1 = 1 and δν 2 = ν = 1/(2p + 1) with an integer p, the value of γ was found to be γ = 3/(2ν + 1) [27]. For simplicity, we neglect any voltage and temperature dependence in g.…”

“…The transmitted contributions δI τ,tr j in Eq. (27) reflect fluctuations in the voltage difference between the channels,…”

“…In general, the topological quantizations (1) and (2) do not hold for edges with counterpropagating modes since the conductances depend on degree of backscattering. However, the quantizations (1) and (2) are restored in the incoherent (fully equilibrated) regime [13,[25][26][27]. The incoherent regime takes place in the limit l eq L, where L is the edge length and l eq is a characteristic length for inelastic equilibration.…”

“…More recently, Refs. 26,27,30, and 31 performed a systematic study of the electric and thermal transport for the incoherent ν B = 2/3 edge. Further, Ref.…”