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Transport and percolation in a low-density high-mobility two-dimensional hole system
M J Manfra1, E H Hwang, S Das Sarma
1Bell Laboratories, Alcatel-Lucent, Murray Hill, New Jersey 07974, USA.
Physical Review Letters
|February 1, 2008
Summary
This study explores resistivity in a high-quality two-dimensional hole system. Findings suggest temperature-dependent screening influences metallic behavior and inhomogeneity drives a transition to an insulating state.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- Investigating the electronic properties of two-dimensional (2D) systems is crucial for understanding quantum phenomena.
- High-quality semiconductor heterostructures enable the study of fundamental physics in reduced dimensions.
Purpose of the Study:
- To examine the temperature and density dependence of resistivity in a high-quality 2D hole system on GaAs.
- To elucidate the mechanisms governing the transition from metallic to insulating behavior.
Main Methods:
- Fabrication of an extremely high quality two-dimensional hole system on the (100) surface of Gallium Arsenide (GaAs).
- Measurements of resistivity as a function of temperature (50-300 mK) and hole density.
- Analysis of conductivity versus density data at a fixed low temperature (50 mK).
Main Results:
- Observed nonmonotonic temperature dependence of resistivity in the metallic regime (p > 4x10^9 cm^-2), consistent with temperature-dependent screening of residual impurities.
- Identified an inhomogeneity-driven percolation-type transition to an insulating state at a critical density of 3.8x10^9 cm^-2 at 50 mK.
Conclusions:
- Temperature-dependent screening plays a significant role in the metallic behavior of high-density 2D hole systems.
- System inhomogeneity and percolation effects are critical in driving the transition to an insulating state at low densities.
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