Intrinsic gap of the nu=5/2 fractional quantum Hall state.
The fractional quantum Hall effect is observed at low magnetic field where the cyclotron energy is smaller than the Coulomb interaction energy. The nu=5/2 excitation gap at 2.63 T is measured to be 262+/-15 mK, similar to values obtained in samples with twice the electronic density. Examining the role of disorder on the 5/2 state, we find that a large discrepancy remains between theory and experiment for the intrinsic gap extrapolated from the infinite mobility limit. The observation of a 5/2 state in the low-field regime suggests that inclusion of nonperturbative Landau level mixing may be necessary to fully understand the energetics of half-filled fractional quantum Hall liquids.
Department of Physics, McGill University, Montreal, H3A 2T8, Canada.
C R
CR
Dean
B A
BA
Piot
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P
Hayden
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S
Das Sarma
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G
Gervais
L N
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Pfeiffer
K W
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West