Dynamic nuclear polarization induced by breakdown of fractional quantum Hall effect

We study dynamic nuclear polarization (DNP) induced by breakdown of the fractional quantum Hall (FQH) effect. We find that voltage-current characteristics depend on current sweep rates at the quantum Hall states of Landau-level filling factors nu=1, 2/3, and 1/3. The sweep-rate dependence is attributed to DNP occurring in the breakdown regime of FQH states. Results of a pump and probe experiment show that the polarity of the DNP induced in the breakdown regimes of the FQH states is opposite to that of the DNP induced in the breakdown regimes of odd-integer quantum Hall states.