Anomalous Gap Reversal of the $3+1/3$ and $3+1/5$ Fractional Quantum Hall States

TL;DR

This study reports the discovery of an energy gap at filling factor 3+1/3, revealing unexpected particle-hole symmetry breaking and an anomalous gap reversal compared to similar states, suggesting a non-conventional origin.

Contribution

It provides experimental evidence of energy gap opening at 3+1/3 and uncovers anomalous gap reversal, challenging existing theories of fractional quantum Hall states.

Findings

Energy gap established at ν=3+1/3

Unexpected particle-hole symmetry breaking observed

Reversal of energy gap magnitudes compared to lower spin branch states

Abstract

In this work we report the opening of an energy gap at the filling factor $\nu=3+1/3$, firmly establishing the ground state as a fractional quantum Hall state. This and other odd-denominator states unexpectedly break particle-hole symmetry. Specifically, we find that the relative magnitudes of the energy gaps of the $\nu=3+1/3$ and $3+1/5$ states from the upper spin branch are reversed when compared to the $\nu=2+1/3$ and $2+1/5$ counterpart states in the lower spin branch. Our findings raise the possibility that the former states have a non-conventional origin.