Finite Temperature Behavior in the Second Landau Level of the Two-dimensional Electron Gas

TL;DR

This study investigates the behavior of the two-dimensional electron gas in the second Landau level at finite temperatures, revealing that most features are due to bubble phases, with some evidence of fractional quantum Hall states at specific filling factors.

Contribution

The paper clarifies the nature of magnetoresistance features in the second Landau level, distinguishing between bubble phases and fractional quantum Hall states, and reports temperature-dependent phase competition.

Findings

Most magnetoresistance features are from bubble phases.

Evidence of incipient fractional quantum Hall states at specific filling factors.

Fractional quantum Hall states collapse at low temperatures due to phase competition.

Abstract

Reports of weak local minima in the magnetoresistance at $\nu=2+3/5$, $2+3/7$, $2+4/9$, $2+5/9$, $2+5/7$, 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 $\nu=2+2/7$ 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.