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Coupling of Josephson currents in quantum Hall bilayers.
X Huang1, W Dietsche, M Hauser
1Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
Physical Review Letters
|October 30, 2012
Summary
Researchers studied bilayer electron gases in a quantized Hall phase, finding identical Josephson currents at the edges. The interlayer excitonic ground state mediates interactions, allowing control of edge currents.
Area of Science:
- Condensed Matter Physics
- Quantum Hall Effect
- Exciton Physics
Background:
- Bilayer two-dimensional electron gases (2DEGs) exhibit complex quantum phenomena.
- The quantized Hall phase at total filling factor one is theorized as a Bardeen-Cooper-Schrieffer-like state of interlayer excitons.
- Corbino devices offer a unique geometry for studying edge and bulk transport in 2DEGs.
Purpose of the Study:
- Investigate the nature of interlayer excitonic states in bilayer 2DEGs.
- Characterize Josephson currents and inter-edge conductance in a Corbino device geometry.
- Explore the control mechanisms of edge Josephson currents mediated by interlayer interactions.
Main Methods:
- Fabrication and measurement of ring-shaped (Corbino) devices using bilayer 2DEGs.
- Probing the quantized Hall phase at total filling factor one.
- Measuring Josephson currents at the device edges and conductance between them.
Main Results:
- Identical Josephson currents were observed at both edges of the Corbino device.
- Negligible conductance was detected between the two edges.
- The maximum Josephson current at one edge could be modulated by a second interlayer Josephson current at the opposite edge.
Conclusions:
- The observed phenomena support the model of a coherent Bardeen-Cooper-Schrieffer-like state of interlayer excitons.
- The neutral interlayer excitonic ground state acts as the mediator for interactions between the edges due to high inter-edge electrical resistance.
- Edge Josephson currents in this system exhibit controllable behavior mediated by interlayer excitonic interactions.
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