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Detecting topological currents in graphene superlattices.
R V Gorbachev1, J C W Song2, G L Yu3
1Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester M13 9PL, UK. School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
Science (New York, N.Y.)
|October 25, 2014
Summary
Topological materials exhibit unique Hall-like currents without magnetic fields. Graphene superlattices show long-range, charge-neutral flow, enabling new valley-based information processing.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Topological materials can generate transverse currents without magnetic fields.
- Graphene superlattices with broken inversion symmetry are predicted to host unique valley-dependent topological currents.
Purpose of the Study:
- To experimentally observe and characterize the predicted long-range, charge-neutral topological currents in graphene superlattices.
- To investigate the potential of these topological currents for future electronic applications.
Main Methods:
- Fabrication of graphene superlattices with broken inversion symmetry.
- Measurement of nonlocal voltages at zero magnetic field near Dirac points.
- Characterization of current strength and gate voltage control.
Main Results:
- Observation of a nonlocal voltage indicative of topological currents at zero magnetic field.
- Detection of these currents over several micrometers, demonstrating long-range transport.
- Topological currents found to be comparable in strength to the applied current, implying large valley-Hall angles.
Conclusions:
- Experimental confirmation of predicted topological currents in graphene superlattices.
- Demonstration of long-range charge-neutral flow and transistor-like control.
- Potential for exploiting valley degrees of freedom in graphene for novel information processing devices.
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