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Negative Coulomb Drag in Double Bilayer Graphene.
J I A Li1, T Taniguchi2, K Watanabe2
1Department of Physics, Columbia University, New York, New York 10027, USA.
Physical Review Letters
|August 6, 2016
Summary
Researchers observed a novel negative Coulomb drag in bilayer-bilayer graphene, distinct from prior findings. Adjusting the device aspect ratio revealed pure momentum drag, matching theoretical predictions.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Electronics
Background:
- Coulomb drag measures electron-electron interactions in layered electronic systems.
- Bilayer graphene offers unique electronic properties compared to monolayer graphene.
- Hexagonal boron nitride serves as an effective dielectric separator in van der Waals heterostructures.
Purpose of the Study:
- To experimentally investigate Coulomb drag in a bilayer-bilayer graphene system.
- To explore the influence of device geometry on drag response.
- To compare experimental results with theoretical predictions for bilayer-bilayer graphene.
Main Methods:
- Fabrication of a double quantum well structure using bilayer graphene and hexagonal boron nitride.
- Low-temperature electrical transport measurements to quantify Coulomb drag.
- Systematic variation of device aspect ratio to isolate different drag components.
Main Results:
- Observation of a novel negative Coulomb drag response at low temperatures and intermediate densities.
- Suppression of the negative drag component by altering the device aspect ratio.
- Recovery of a response consistent with pure momentum drag, matching theoretical models.
Conclusions:
- The observed negative drag is a distinct phenomenon in bilayer-bilayer graphene, differing from monolayer systems.
- Device geometry plays a crucial role in determining the dominant drag mechanism.
- Experimental findings provide strong validation for theoretical predictions of momentum drag in this specific heterostructure.
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