Transport and tunneling within a compressible electron liquid in wires and rings ofGaAs/AlxGa1−xAsheterostructures

Abstract

A detailed study of low-temperature magnetoconductance in between $\ensuremath{\nu}=2$ and $\ensuremath{\nu}=3$ quantized Hall plateaus is presented. The data are obtained for disordered two-terminal submicron wires and rings defined in ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ heterostructures modulation doped by Si. In the region between the plateaus, electron density of compressible liquid in the central current strip increases gradually when lowering the magnetic field. At low densities of the electrons in the strip, a sequence of peaks is detected in the dependence of conductance on the magnetic field. This unexpected effect is interpreted in terms of the Coulomb blockade associated with the charging of the current strip. In the same range of the magnetic fields, a temperature dependence of conductance, together with the absence of the Aharonov-Bohm oscillations for transport along the central strip in the ring, are taken as the evidence for an enhancement of the electron-phonon scattering rate at the percolation threshold. The frequency doubling of the Aharonov-Bohm oscillations in a ring with an additional potential barrier is discussed in terms of the phase concept. Slow time evolution of conductance is observed for higher concentrations of the electrons in the current strip. This surprising noise is attributed to glassy dynamics of localized electrons in the wire center, and to the corresponding time dependence of the impurity-assisted tunneling probability between the current carrying regions.