Non-Equilibrated Counter Propagating Edge Modes in the Fractional Quantum Hall Regime

Abstract

It is well established that 'density reconstruction' at the edge of a two dimensional electron gas takes place for 'hole-conjugate' states in the fractional quantum Hall effect (such as $\nu =2/3,3/5,$ etc.). Such reconstruction leads, after equilibration between counter propagating edge channels, to a downstream chiral current edge mode accompanied by upstream chiral neutral modes (carrying energy without net charge). Short equilibration length prevented thus far observation of the counter propagating current channels - the hallmark of density reconstruction. Here, we provide evidence for such non-equilibrated counter-propagating current channels, in short regions $(l=4\mu m$ and $l=0.4\mu m)$ of fractional filling $\nu =2/3$, and, unexpectedly, $\nu =1/3$, sandwiched between two regions of integer filling $\nu =1$. Rather than a two-terminal fractional conductance, the conductance exhibited a significant ascension towards unity quantum conductance $(G_Q=e^2/h)$ at or near the fractional plateaus. We attribute this conductance rise to the presence of a non-equilibrated downstream $\nu =1$ channel in the fractional short regions.

9 pages, 4 figures, supplemental material

References in corpus (2)

• Observation of neutral modes in the fractional quantum Hall regime
• Extracting net current from an upstream neutral mode in the fractional quantum Hall regime

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