Finite-temperature behavior in the second Landau level of the two-dimensional electron gas

Reports of weak local minima in the magnetoresistance at ν=2+3/5, 2+3/7, 2+4/9, 2+5/9, 2+5/7, and 2+5/8 in the second Landau level of the electron gas in GaAs/AlGaAs left open the possibility of fractional quantum Hall states at these filling factors. In a high-quality sample we found that the magnetoresistance exhibits peculiar features near these filling factors of interest. These features, however, cannot be associated with fractional quantum Hall states; instead, they originate from magnetoresistive fingerprints of the electronic bubble phases. We found only two exceptions: at ν=2+2/7 and 2+5/7 there is evidence for incipient fractional quantum Hall states at intermediate temperatures. As the temperature is lowered, these fractional quantum Hall states collapse due to a phase competition with bubble phases.