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Electric-field tuned second harmonic generation in twisted bilayer graphene
Optics Express
|August 13, 2025
Summary
We theoretically investigated second harmonic generation (SHG) in twisted bilayer graphene (tBLG). Decreasing twist angle and applying electric fields significantly enhance SHG, offering tunable optoelectronic device possibilities.
Area of Science:
- Nonlinear Optics
- Condensed Matter Physics
- Materials Science
Background:
- Twisted bilayer graphene (tBLG) exhibits unique electronic properties due to interlayer coupling and twist angle.
- Nonlinear optical effects like second harmonic generation (SHG) are crucial for optoelectronic applications.
- Understanding twist angle and electric field effects on SHG in tBLG is key for device design.
Purpose of the Study:
- To theoretically investigate the twist angle-dependent and electric field-controlled second harmonic generation (SHG) in twisted bilayer graphene (tBLG).
- To provide a quantitative explanation for observed SHG effects in tBLG and explore new control mechanisms.
- To assess the potential of tBLG for tunable optoelectronic devices.
Main Methods:
- Utilized a four-band continuum model and independent-particle approximation for theoretical analysis.
- Investigated SHG susceptibility based on one-photon and two-photon resonant interband transitions.
- Analyzed the impact of varying twist angles and external electric fields on SHG properties.
Main Results:
- SHG susceptibility in tBLG reaches up to 10^3 pm^2/V and increases as twist angle decreases.
- External electric fields can enhance SHG susceptibility by over an order of magnitude.
- Electric fields tune absorption peaks and SHG magnitude by manipulating Dirac cones and van Hove singularities.
Conclusions:
- The study provides a theoretical framework explaining twist angle-dependent SHG in tBLG.
- Electric field control offers a pathway for wide-band tunability and high-performance optoelectronic devices.
- Findings offer valuable insights for designing novel photonic and electronic devices based on tBLG.
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