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Control over topological insulator photocurrents with light polarization
J W McIver1, D Hsieh, H Steinberg
1Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nature Nanotechnology
|December 6, 2011
Summary
Illuminating topological insulators with polarized light generates photocurrents from unique spin-polarized surface states. This discovery opens avenues for exploring dynamic topological properties and developing new opto-spintronic devices.
Area of Science:
- Condensed Matter Physics
- Quantum Materials
- Materials Science
Background:
- Three-dimensional topological insulators possess unique spin-polarized surface states robust against backscattering.
- Static electronic properties of these states are well-characterized, but dynamic responses to light remain largely unexplored.
- Theoretical proposals suggest light-induced topological quantum phase transitions and spin-polarized currents.
Purpose of the Study:
- To experimentally investigate the effects of optically driving topological insulators out of equilibrium.
- To measure photocurrents generated in topological insulators under illumination.
- To explore the origin and characteristics of light-induced photocurrents in topological insulators.
Main Methods:
- Illumination of the topological insulator Bismuth Selenide (Bi2Se3) with circularly and linearly polarized light.
- Measurement and analysis of generated photocurrents.
- Correlation of photocurrent direction and magnitude with light polarization and helicity.
Main Results:
- Observation of photocurrent generation in Bi2Se3 upon illumination with circularly polarized light.
- Demonstration that photocurrent direction reverses with the helicity of the light, originating from topological helical Dirac fermions.
- Detection of a polarization-controlled photocurrent potentially linked to topological surface states.
Conclusions:
- Optically driving topological insulators can generate measurable photocurrents.
- These photocurrents provide a new experimental probe for the dynamic properties of topological surface states.
- The findings pave the way for novel opto-spintronic devices based on topological insulators.
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