10,711 research outputs found
Current-induced nuclear-spin activation in a two-dimensional electron gas
Electrically detected nuclear magnetic resonance was studied in detail in a
two-dimensional electron gas as a function of current bias and temperature. We
show that applying a relatively modest dc-current bias, I_dc ~ 0.5 microAmps,
can induce a re-entrant and even enhanced nuclear spin signal compared with the
signal obtained under similar thermal equilibrium conditions at zero current
bias. Our observations suggest that dynamic nuclear spin polarization by small
current flow is possible in a two-dimensional electron gas, allowing for easy
manipulation of the nuclear spin by simple switching of a dc current.Comment: 5 pages, 3 fig
Nonconventional odd denominator fractional quantum Hall states in the second Landau level
We report the observation of a new fractional quantum Hall state in the
second Landau level of a two-dimensional electron gas at the Landau level
filling factor . We find that the model of noninteracting composite
fermions can explain the magnitude of gaps of the prominent 2+1/3 and 2+2/3
states. The same model fails, however, to account for the gaps of the 2+2/5 and
the newly observed 2+6/13 states suggesting that these two states are of exotic
origin.omposite fermion model. However, the weaker 2+2/5 and 2+6/13 states
deviate significantly suggesting that these states are of exotic origin
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