Electron-Electron Interactions and the Paired-to-Nematic Quantum Phase Transition in the Second Landau Level

TL;DR

This study investigates the pressure- and interaction-tuned quantum phase transition between paired and nematic states in the second Landau level of a two-dimensional electron gas, revealing electron-electron interactions as a key factor.

Contribution

It demonstrates that electron-electron interactions, not just pressure, drive the paired-to-nematic transition in the second Landau level, extending understanding of quantum phase competition.

Findings

Pressure induces a paired-to-nematic transition at both ν=5/2 and ν=7/2.

Similar transitions occur at ambient pressure when interactions are tuned.

Electron-electron interactions are crucial in controlling the phase transition.

Abstract

In spite of its ubiquity in strongly correlated systems, the competition of paired and nematic ground states remains poorly understood. Recently such a competition was reported in the two-dimensional electron gas at filling factor $\nu=5/2$. At this filling factor a pressure-induced quantum phase transition was observed from the paired fractional quantum Hall state to the quantum Hall nematic. Here we show that the pressure induced paired-to-nematic transition also develops at $\nu=7/2$, demonstrating therefore this transition in both spin branches of the second orbital Landau level. However, we find that pressure is not the only parameter controlling this transition. Indeed, ground states consistent with those observed under pressure also develop in a sample measured at ambient pressure, but in which the electron-electron interaction was tuned close to its value at the quantum critical point. Our experiments suggest that electron-electron interactions play a critical role in driving the paired-to-nematic transition.