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Published on: November 30, 2012
Optical second-harmonic generation from two-dimensional hexagonal crystals with broken space inversion symmetry
Vl A Margulis1, E E Muryumin, E A Gaiduk
1Department of Physics, Mordovian Ogarev State University, Saransk 430005, Russia.
Summary
We developed a theory for optical second-harmonic generation (SHG) in 2D honeycomb materials. Trigonal warping effects significantly enhance SHG, suggesting applications in optoelectronics.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nonlinear Optics
Background:
- Two-dimensional (2D) honeycomb lattice structures, like graphene on SiC and hexagonal boron nitride (h-BN), exhibit broken space inversion symmetry.
- Optical second-harmonic generation (SHG) is a nonlinear optical process sensitive to material symmetry.
Purpose of the Study:
- To develop a microscopic theory for SHG in 2D honeycomb materials.
- To investigate the role of π-electron dynamics and electronic band structure in SHG.
- To explore the potential of SHG as a probe for 2D materials and their optoelectronic applications.
Main Methods:
- Utilized a two-band π-electron tight-binding model.
- Applied the Genkin-Mednis formalism for second-order nonlinear optical response.
- Derived an explicit expression for the SHG susceptibility (χ2(SHG(ω)).
Main Results:
- SHG susceptibility arises from interband and intraband π-electron motion.
- Trigonal warping of energy bands significantly enhances SHG, contrary to simplified models.
- Calculated SHG susceptibility reaches 10⁻⁴ esu for graphene/SiC and 10⁻⁷ esu for h-BN near half the bandgap.
Conclusions:
- SHG is a sensitive probe of the electronic structure in 2D hexagonal crystals.
- These materials show promise for optoelectronic nano-devices due to their nonlinear optical properties.
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