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Terahertz radiation driven chiral edge currents in graphene
Physical Review Letters
|January 17, 2012
Summary
Circularly polarized terahertz radiation induces edge photocurrents in graphene, forming a vortex whose direction reverses with light helicity. This phenomenon reveals insights into graphene
Area of Science:
- Condensed Matter Physics
- Materials Science
- Optoelectronics
Background:
- Single-layer graphene exhibits unique electronic properties.
- Interactions between light and materials at the nanoscale are crucial for device development.
- Edge effects in low-dimensional materials can significantly alter their behavior.
Purpose of the Study:
- To investigate photocurrent generation in graphene edges using terahertz radiation.
- To explore the influence of light polarization on induced photocurrents.
- To establish a method for characterizing graphene edge properties.
Main Methods:
- Illumination of single-layer graphene edges with circularly polarized terahertz (THz) radiation at normal incidence.
- Measurement of induced photocurrents along the graphene sample edges.
- Development of a theoretical model based on Boltzmann's kinetic equation.
Main Results:
- Observation of vortex photocurrents flowing along graphene edges.
- Reversal of photocurrent vortex direction upon switching light helicity (left to right-handed).
- Demonstration that edge asymmetry and radiation electric field drive carrier scattering, causing the photocurrent.
- Good agreement between experimental results and theoretical predictions.
Conclusions:
- Graphene edge photocurrents are induced by circularly polarized THz radiation.
- The observed photocurrents are a direct consequence of reduced spatial symmetry at the edges.
- Edge photocurrents offer a novel method for determining carrier conductivity type and momentum scattering time in graphene.
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