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In this work we report the opening of an energy gap at the filling factor $ u=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 $ u=3+1/3$ and $3+1/5$ states from the upper spin branch are reversed when compared to the $ u=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.
We study the quantum phase transitions of frustrated antiferromagnetic Heisenberg spin-1 systems on the 3/4 and 3/5 skewed two leg ladder geometries. These systems can be viewed as arising by periodically removing rung bonds from a zigzag ladder. We
We report on magnetotransport measurements of multi-terminal suspended graphene devices. Fully developed integer quantum Hall states appear in magnetic fields as low as 2 T. At higher fields the formation of longitudinal resistance minima and transve
^139La nuclear magnetic resonance studies reveal markedly different magnetic properties of the two sites created by the charged domain wall formation in La_(5/3)Sr_(1/3)NiO_4. NMR is slow compared to neutron scattering; we observe a 30 K suppression
The Hamiltonian Theory of the fractional quantum Hall (FQH) regime provides a simple and tractable approach to calculating gaps, polarizations, and many other physical quantities. In this paper we include disorder in our treatment, and show that a si
We investigate the nature of the fractional quantum Hall (FQH) state at filling factor $ u=13/5$, and its particle-hole conjugate state at $12/5$, with the Coulomb interaction, and address the issue of possible competing states. Based on a large-scal