Surface acoustic wave propagation and inhomogeneities in low-density two-dimensional electron systems near the metal–insulator transition
نویسنده
چکیده
We have measured the surface acoustic wave velocity shift in a GaAs/AlGaAs heterostructure containing a two-dimensional electron system (2DES) in a low-density regime (!10 cm) at zero magnetic field. The interaction of the surface acoustic wave with the 2DES is not well described by a simple model using low-frequency conductivity measurements. We speculate that this conflict is a result of inhomogeneities in the 2DES, which become very important at low density. This has implications for the putative metal–insulator transition in two dimensions. q 2005 Elsevier Ltd. All rights reserved. PACS: 71.30.Ch; 73.40.Kc; 72.50.Cb
منابع مشابه
Metal-Insulator Transition in a Low-Mobility Two-Dimensional Electron System
We have varied the disorder in a two-dimensional electron system in silicon by applying substrate bias. When the disorder becomes sufficiently low, we observe the emergence of the metallic phase, and find evidence for a metal-insulator transition (MIT): the single-parameter scaling of conductivity with temperature near a critical electron density. We obtain the scaling function β, which determi...
متن کاملMetal-Insulator and Superconductor-Insulator Transitions in Correlated Electron Systems
Quantum transitions between the Mott insulator and metals by controlling filling in two-dimensional square lattice are characterized by a large dynamical exponent z = 4 where the origin of unusual metallic properties near the Mott insulator are ascribed to the proximity of the transition. The scaling near the transition indicates the formation of flat dispersion area due to singular momentum de...
متن کاملMetal-insulator transition in disordered two-dimensional electron systems.
We present a theory of the metal-insulator transition in a disordered two-dimensional electron gas. A quantum critical point, separating the metallic phase, which is stabilized by electronic interactions, from the insulating phase, where disorder prevails over the electronic interactions, has been identified. The existence of the quantum critical point leads to a divergence in the density of st...
متن کاملQuantum phase transitions in one-dimensional electron-phonon systems
Low dimensional strongly coupled electron-phonon systems like MX-chains, ferroelectric perovskites, conjugated polymers, or organic charge transfer salts exhibit a remarkable wide range of strengths of competing forces and, as a result, physical properties [1]. Most notably quasi one-dimensional (1D) materials are very susceptible to structural distortions driven by the electron-phonon (EP) int...
متن کاملThermodynamic density of states of two-dimensional GaAs systems near the apparent metal-insulator transition.
We perform combined resistivity and compressibility studies of two-dimensional hole and electron systems which show the apparent metal-insulator transition--a crossover in the sign of deltaR/deltaT with changing density. No thermodynamic anomalies have been detected in the crossover region. Instead, despite a tenfold difference in r(s), the compressibility of both electrons and holes is well de...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2005