Measuring Hall viscosity of graphene's electron fluid
A I Berdyugin1, S G Xu1,2, F M D Pellegrino3,4
1School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
Science (New York, N.Y.)
|March 2, 2019
Summary
Researchers observed a new Hall effect in viscous graphene, where the electron fluid generates an opposing electric field. This viscous Hall effect, previously theoretical, was experimentally measured for the first time.
Area of Science:
- Condensed matter physics
- Materials science
Background:
- The Hall effect describes the production of a voltage difference across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current.
- Standard Hall effect measurements are crucial for characterizing electronic properties of materials.
- Theoretical predictions suggested the existence of Hall viscosity in certain electron systems, but experimental evidence remained elusive.
Purpose of the Study:
- To investigate the behavior of electrical conductors with high viscosity under magnetic fields.
- To identify and characterize deviations from the standard Hall effect in viscous electron systems.
- To experimentally measure Hall viscosity, a predicted but unobserved transport coefficient.
Main Methods:
- Studying the response of viscous electron fluid in graphene to nonquantizing magnetic fields.
- Analyzing local voltages near current-injecting contacts to identify viscous contributions.
- Conducting experiments over a wide range of temperatures and carrier densities.
Main Results:
- Observed a qualitative deviation from the standard Hall effect in viscous graphene.
- Identified an electric field generated by the viscous electron fluid that opposes the ordinary Hall effect.
- Successfully extracted the Hall viscosity coefficient from experimental data.
Conclusions:
- The viscous Hall effect in graphene is a substantial phenomenon that deviates from standard Hall effect behavior.
- Hall viscosity can be experimentally measured in highly viscous electron systems like graphene.
- This finding provides the first experimental evidence for the elusive Hall viscosity coefficient.
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