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Band Nesting in Two-Dimensional Crystals: An Exceptionally Sensitive Probe of Strain.
Lukas Mennel1, Valerie Smejkal2, Lukas Linhart2
1Vienna University of Technology, Institute of Photonics, Gußhausstraße 27-29, 1040 Vienna, Austria, EU.
Nano Letters
|May 22, 2020
Summary
Band nesting in 2D materials enhances optical response. Researchers used this to precisely measure strain in transition metal dichalcogenides (TMDs) via optical second harmonic generation (SHG), revealing high strain sensitivity.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Optics
Background:
- Band nesting, where electronic bands are equispaced, creates joint density of states singularities.
- These singularities lead to enhanced optical responses in two-dimensional (2D) materials.
- This phenomenon is sensitive to changes in the material's band structure.
Purpose of the Study:
- To exploit band nesting for sensitive strain detection in semiconducting transition metal dichalcogenides (TMDs).
- To measure and theoretically analyze the nonlinear photoelastic effect in atomically thin TMDs.
- To investigate the energy-dependent nonlinear optical response related to band nesting.
Main Methods:
- Measurement of polarization-resolved optical second harmonic generation (SHG) at band nesting energies.
- Calculation of SHG and theoretical analysis of the nonlinear photoelastic effect.
- Study of strain effects on atomically thin MoS2, MoSe2, WS2, and WSe2.
Main Results:
- Demonstrated strong, energy-dependent modulation of SHG under strain.
- Observed good qualitative agreement between experimental measurements and theoretical predictions.
- Attributed the high sensitivity to strain-induced redistribution of the joint density of states.
Conclusions:
- The nonlinear photoelastic effect in 2D TMDs is strongly energy-dependent and sensitive to strain.
- Band nesting provides a powerful mechanism for sensitive strain probing in 2D materials.
- This strain sensitivity is predicted to be a general property of 2D materials exhibiting band nesting.
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