Developing fractional quantum Hall states at even-denominator fillings 1/6 and 1/8

TL;DR

This paper reports the experimental observation of developing fractional quantum Hall states at even-denominator fillings 1/6 and 1/8 in ultrahigh-quality two-dimensional electron systems, suggesting potential non-Abelian anyon excitations.

Contribution

It demonstrates the emergence of FQHSs at 1/6 and 1/8 fillings, a novel finding in the context of quantum Hall physics, indicating possible new non-Abelian states.

Findings

Observation of magnetoresistance minima at 1/6 and 1/8

Evidence of composite fermion pairing at these fillings

Potential for non-Abelian anyon excitations

Abstract

In the extreme quantum limit, when the Landau level filling factor $\nu<1$, the dominant electron-electron interaction in low-disorder two-dimensional electron systems leads to exotic many-body phases. The ground states at even-denominator $\nu=$ 1/2 and 1/4 are typically Fermi seas of composite fermions carrying two and four flux quanta, surrounded by the Jain fractional quantum Hall states (FQHSs) at odd-denominator fillings $\nu=p/(2p\pm1)$ and $\nu=p/(4p\pm1)$, where $p$ is an integer. For $\nu<$ 1/5, an insulating behavior, which is generally believed to signal the formation of a pinned Wigner crystal, is seen. Our experiments on ultrahigh-quality, dilute, GaAs two-dimensional electron systems reveal developing FQHSs at $\nu=p/(6p\pm1)$ and $\nu=p/(8p\pm1)$, manifested by magnetoresistance minima superimposed on the insulating background. In stark contrast to $\nu=$ 1/2 and 1/4, however, we observe a pronounced, sharp minimum in magnetoresistance at $\nu=$ 1/6 and a somewhat weaker minimum at $\nu=$ 1/8, suggesting developing FQHSs, likely stabilized by the pairing of composite fermions that carry six and eight flux quanta. Our results signal the unexpected entry, in ultrahigh-quality samples, of FQHSs at even-denominator fillings 1/6 and 1/8, which are likely to harbor non-Abelian anyon excitations.