Extracting net current from an upstream neutral mode in the fractional quantum Hall regime

Abstract

Upstream neutral modes, counter propagating to charge modes and carrying energy without net charge, had been predicted to exist in some of the fractional quantum Hall states and were recently observed via noise measurements. Understanding such modes will assist in identifying the wavefunction of these states, as well as shedding light on the role of Coulomb interactions within edge modes. Here, operating mainly in the n ¼ 2/3 state, we place a quantum dot a few micrometres upstream of an ohmic contact, which serves as a 'neutral modes source'. We show that the neutral modes heat the input of the dot, causing a net thermo-electric current to flow through it. Heating of the electrons leads to a decay of the neutral mode, manifested in the vanishing of the thermo-electric current at T4110 mK. This set-up provides a straightforward method to investigate upstream neutral modes without turning to the more cumbersome noise measurements.

Creating topological interfaces and detecting chiral edge modes in a two-dimensional optical lattice

“…Interestingly, such geometries have been considered to probe the fractional (anyonic) statistics of FQH excitations [33]. More recent experiments also revealed signatures of exotic counter-propagating ("neutral upstream") modes in FQH liquids [29][30][31][32], in agreement with early theoretical works [23][24][25][26].…”

“…For instance, FQH liquids potentially exhibit counter-propagating edge modes (allowing back-scattering on the edge in the presence of impurities), while still presenting a finite and quantized Hall conductivity [23][24][25][26]32]. While these counter-propagating modes remained undetectable in standard edge-magnetoplasma experiments [21,23], they were recently revealed through shot noise [29,31,32] and thermometry [30] measurements. Even more recently, it was suggested in Ref.…”

“…Detecting and analyzing the properties of topological edge excitations constitutes an intense field of research since the early days of the QH effect [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. The chiral nature of QH edge modes was first revealed through edge-magnetoplasma experiments [21] (see also the pioneer measurements reported in Refs.…”

Edge reconstruction in fractional quantum Hall states

“…In that model, depicted in Fig. 1a III, the inner three edge channels were expected to renormalize to a single downstream charge mode with conductance 1 On the experimental front, recent observations of upstream neutral modes [6,7,14,15,16] supported the KFP model of the = 2 3 state [5]. However, Bid et al [17], while studying partitioning of the downstream charge channel for = 2 3 in a quantum point contact (QPC), ) with strong noise.…”

Topological Quantum Computation with Non-Abelian Anyons in Fractional Quantum Hall States

“…5 The Pfaffian state: comparison with the experiment at ν H = 2/3 A recent experiment [31] brought a new hope for the possibility to measure some thermoelectric characteristics of SETs and eventually detect "upstream neutral modes" in the fractional quantum Hall regime. In this section we will calculate and plot the conductance, thermopower and thermoelectric power factor for the Pfaffian FQH state and will compare these quantities with the measured ones in the experiment [31].…”