Giant frictional drag in strongly interacting bilayers near filling factor one

TL;DR

This paper reports extremely large frictional drag in strongly interacting bilayer GaAs systems near filling factor one, indicating phase separation and complex quantum Hall state transitions.

Contribution

It provides the first detailed measurements of giant frictional drag near the $ u=1$ quantum Hall state in bilayer systems, supporting phase separation models.

Findings

Longitudinal drag resistivity exceeds 15 kΩ/□ at $ u=1.15$

Drag resistivity shows weak temperature dependence and saturates at low temperatures

Results support phase separation models with puddles of $ u=1$ QHS

Abstract

We study the frictional drag in high mobility, strongly interacting GaAs bilayer hole systems in the vicinity of the filling factor $\nu=1$ quantum Hall state (QHS), at the same fillings where the bilayer resistivity displays a reentrant insulating phase. Our measurements reveal a very large longitudinal drag resistivity ($\rho^{D}_{xx}$) in this regime, exceeding 15 k$\Omega/\Box$ at filling factor $\nu=1.15$. $\rho^{D}_{xx}$ shows a weak temperature dependence and appears to saturate at a finite, large value at the lowest temperatures. Our observations are consistent with theoretical models positing a phase separation, e.g. puddles of $\nu=1$ QHS embedded in a different state, when the system makes a transition from the coherent $\nu=1$ QHS to the weakly coupled $\nu=2$ QHS.