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Many-body localization study in low-density electron gases: do metals exist in two dimensions?
Geneviève Fleury1, Xavier Waintal
1Nanoelectronics group, Service de Physique de l'Etat Condensé, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France.
Physical Review Letters
|December 31, 2008
Summary
Electron interactions in disordered two-dimensional electron gases (2DEGs) cause delocalization. This effect significantly increases the localization length, especially in systems with valley degeneracy, explaining observed metallic behavior.
Area of Science:
- Condensed Matter Physics
- Quantum Mechanics
- Materials Science
Background:
- Disordered two-dimensional electron gases (2DEGs) exhibit complex electronic properties.
- The role of Coulomb interactions in electron localization in 2DEGs is a key research question.
- Understanding localization length is crucial for predicting material conductivity.
Purpose of the Study:
- To systematically investigate the impact of Coulomb interaction on the localization length of disordered 2DEGs.
- To explore the influence of valley degeneracy on electron delocalization.
- To elucidate the mechanism behind the metallic behavior observed in these systems.
Main Methods:
- Utilized ground state quantum Monte Carlo simulations.
- Employed finite size scaling techniques for analysis.
- Studied systems with and without valley degeneracy.
Main Results:
- Coulomb interactions were found to delocalize the 2D system.
- A finite increase in localization length was observed in the absence of valley degeneracy (e.g., GaAs heterostructures).
- A dramatic increase in localization length occurred in the presence of valley degeneracy (e.g., Si metal-oxide-semiconductor field-effect transistors).
Conclusions:
- A simple mechanism explains the metallic behavior in 2DEGs, driven by electron interactions.
- The observed metallic behavior is a genuine effect of interactions.
- The system does not represent a "true" metal in the thermodynamic sense, despite interaction-driven delocalization.
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