Crossover between localized states and pinned Wigner crystal in high-mobility n-GaAs/AlGaAs heterostructures near filling factor $\nu =1$

Abstract

We have measured magnetic field dependences of the attenuation and velocity of surface acoustic waves in a high-mobility $n$-GaAs/AlGaAs structure with a wide quantum well. The results allowed us to find the complex conductance, $\sigma (\omega )$, of the heterostructure for different frequencies, temperatures and magnetic fields near filling factors $\nu =1,2$. Observed behavior of $\sigma (\omega )$ versus magnetic field outside close vicinities of integer fillings reveals an oscillation pattern indicative of the rich fractional quantum Hall effect. Our result is that in very close vicinities of integer filling factors the AC response of a high-mobility two-dimensional structures behaves as that of a two-dimensional system of localized electrons. Namely, both real and imaginary parts of the complex AC conductance at low temperatures agree with the predictions for the two-site model for a two-dimensional hopping system. Another result is the specific temperature dependences of $\sigma (\omega )$, which are extremely sensitive to the filling factor value. These dependences indicate a sharp crossover between the localized modes and a pinned Wigner crystal.

6 pages, 5 figures

References in corpus (4)

• Microwave Resonance of 2D Wigner Crystal around integer Landau fillings
• Microwave spectroscopic observation of distinct electron solid phases in wide quantum wells
• Contactless Measurement of AC Conductance in Quantum Hall Structures
• Dynamics of disordered quantum Hall crystals

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• Competing Fractional Quantum Hall and Electron Solid Phases in Graphene
• Flip-chip gate-tunable acoustoelectric effect in graphene
• Particle-Hole Symmetry and the Reentrant Integer Quantum Hall Wigner Solid
• Magnetotransport patterns of collective localization near $\nu =1$ in a high-mobility two-dimensional electron gas
• Interaction between Surface Acoustic Wave and Quantum Hall Effects
• Charge metastability and hysteresis in the quantum Hall regime
• Thermal Activation Signatures of the Anderson Insulator and the Wigner Solid forming near $\nu =1$
• Density Dependence of the Phases of the $\nu =1$ Integer Quantum Hall Plateau in Low Disorder Electron Gases
• Coexistence of two hole phases in high-quality $p$-GaAs/AlGaAs in the vicinity of Landau level filling factors $\nu$=1 and $\nu$=(1/3)