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

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 $ν=2/3, 3/5,$ 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 $(l=4μm$ and $l=0.4μm)$ of fractional filling $ν=2/3$, and, unexpectedly, $ν=1/3$, sandwiched between two regions of integer filling $ν=1$. 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 $ν=1$ channel in the fractional short regions.

No reviews yet.

No comments yet.