Measurements of Composite Fermion Conductivity Dependence on Carrier Density

Abstract

We present the first experimental study of the carrier density dependence of the composite fermion conductivity ${\sigma }_{xx}^{CF}$ at Landau level filling factors $\nu =1/2$ and $\nu =3/2$ in high-quality front-gated GaAs/Al${}_{0.33}$Ga${}_{0.67}$As heterostructures. Extracting $\alpha$ from the power law ln$({\sigma }_{xx}^{CF})\propto$ ln$(n_e{)}^{\alpha }$ shows that $\alpha \approx 1$. The measured $\alpha \approx 1$ is placed between the predicted value 3/4 in the strong random magnetic field regime, and 3/2 in the weak random magnetic field regime. Comparisons between our results and theory are discussed.

6 pages, 7 figures. We present the first experimental study of the carrier density dependence of the composite fermion conductivity ${\sigma }_{xx}^{CF}$ at Landau level filling factors $\nu =1/2$ and $\nu =3/2$ in high-quality front-gated GaAs/Al${}_{0.33}$Ga${}_{0.67}$As heterostructures