Anomalous Gap Reversal of the $3+1/3$ and $3+1/5$ Fractional Quantum   Hall States
  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. 
Ethan Kleinbaum, Ashwani Kumar, L.N. Pfeiffer, K.W. West, G.A.   Cs\'athy
cond-mat.str-el cond-mat.mes-hall