Scaling of an anomalous metal-insulator transition in a two-dimensional system in silicon atB=0

Abstract

We have studied the temperature dependence of resistivity, ρ, for a two-dimensional electron system in silicon at low electron densities ${\mathit{n}}_{\mathit{s}}$∼${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}2}$, near the metal-insulator transition. The resistivity was empirically found to scale with a single parameter ${\mathit{T}}_0$, which approaches zero at some critical electron density ${\mathit{n}}_{\mathit{c}}$ and increases as a power ${\mathit{T}}_0$∝‖${\mathit{n}}_{\mathit{s}}$-${\mathit{n}}_{\mathit{c}}$ ${\mathrm{\Vert }}^{\mathrm{\beta }}$ with β=1.6±0.1 both in metallic (${\mathit{n}}_{\mathit{s}}$>${\mathit{n}}_{\mathit{c}}$) and insulating (${\mathit{n}}_{\mathit{s}}$<${\mathit{n}}_{\mathit{c}}$) regions. This dependence was found to be sample independent. We have also studied the diagonal resistivity at Landau-level filling factor ν=3/2, where the system is known to be in a true metallic state at high magnetic field and in an insulating state at low magnetic field. The temperature dependencies of resistivity at B=0 and ν=3/2 were found to be identical. These behaviors suggest a true metal-insulator transition in the two-dimensional electron system in silicon at B=0, in contrast with the well-known scaling theory.