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Anomalous coulomb drag in electron-hole bilayers.
A F Croxall1, K Das Gupta, C A Nicoll
1Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Physical Review Letters
|December 31, 2008
Summary
Coulomb drag measurements reveal unexpected upturns and asymmetries in electron-hole bilayers, challenging standard Fermi-liquid theory. These findings contradict Onsager
Area of Science:
- Condensed Matter Physics
- Quantum Materials
- Electron-Hole Systems
Background:
- Electron-hole bilayers are crucial for studying correlated quantum phenomena.
- Understanding interlayer interactions is key to novel electronic states.
- Previous theories predicted specific behaviors in these systems.
Purpose of the Study:
- To investigate Coulomb drag phenomena in GaAs-AlGaAs electron-hole bilayers.
- To identify deviations from established Fermi-liquid theory.
- To explore the nature of correlated phases and interlayer coupling.
Main Methods:
- Performed Coulomb drag measurements at low temperatures (below 1 K).
- Utilized GaAs-AlGaAs heterostructures with varying barrier thicknesses (10 and 25 nm).
- Analyzed drag response in both electron and hole layers within the linear response regime.
Main Results:
- Observed an upturn (potentially followed by a downturn) in the hole layer drag.
- Found significantly weaker or absent drag in the electron layer.
- Experimental results contradicted Onsager's reciprocity theorem, suggesting novel physics.
Conclusions:
- Standard Fermi-liquid theory fails to explain the observed drag behaviors.
- The findings suggest the presence of correlated phases not predicted by current models.
- Further theoretical and experimental work is needed to understand these discrepancies.
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