Electron correlation in the second Landau level; a competition between many, nearly degenerate quantum phases

TL;DR

This study investigates the complex electron behaviors in the second Landau level at ultra-low temperatures, revealing competing quantum phases, insulating states, and potential new fractional quantum Hall states.

Contribution

It provides detailed experimental evidence of multiple competing quantum phases and suggests the possible existence of new even-denominator fractional quantum Hall states.

Findings

Observation of a fully developed ν=2+2/5 state

Identification of insulating phases separating quantum states

Detection of a plateau at ν=2+3/8 indicating potential new states

Abstract

At a very low temperature of 9mK, electrons in the 2nd Landau level of an extremely high mobility two-dimensional electron system exhibit a very complex electronic behavior. With varying filling factor, quantum liquids of different origins compete with several insulating phases leading to an irregular pattern in the transport parameters. We observe a fully developed $\nu=2+2/5$ state separated from the even-denominator $\nu=2+1/2$ state by an insulating phase and a $\nu=2+2/7$ and $\nu=2+1/5$ state surrounded by such phases. A developing plateau at $\nu=2+3/8$ points to the existence of other even-denominator states.