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Resonant Second-Harmonic Generation as a Probe of Quantum Geometry
Pankaj Bhalla1,2,3, Kamal Das4, Dimitrie Culcer3,5
1Department of Physics, School of Engineering and Sciences, SRM University AP, Amaravati, 522240, India.
Physical Review Letters
|December 9, 2022
Summary
Second harmonic generation reveals crucial electronic properties like Berry curvature in solids. This nonlinear optical technique uncovers novel resonances in doped materials, offering new insights into topological and band geometric characteristics.
Area of Science:
- Condensed Matter Physics
- Nonlinear Optics
- Materials Science
Background:
- Nonlinear optical responses are vital for probing solid-state topology and band geometry.
- Second harmonic generation (SHG) is a key nonlinear optical phenomenon.
Purpose of the Study:
- To establish second harmonic generation as a sensitive probe of Berry curvature, quantum metric, and quantum geometric connection.
- To generalize SHG theory for metallic systems, incorporating Fermi surface effects and finite scattering timescales.
Main Methods:
- Generalized theoretical framework for second harmonic generation.
- Inclusion of Fermi surface and Fermi sea effects in metallic systems.
- Analysis of resonance phenomena and novel contributions to the SHG signal.
Main Results:
- Identified SHG as a probe for Berry curvature, quantum metric, and quantum geometric connection.
- Developed a generalized SHG theory including Fermi surface effects and scattering timescales.
- Discovered two new contributions to SHG: a Fermi surface-induced double resonance and a Fermi sea-induced higher-order pole.
Conclusions:
- Second harmonic generation is a powerful tool for characterizing topological and geometric properties of solids.
- The generalized theory predicts observable resonances in doped materials.
- Experimental observations in WTe2 and CuMnAs demonstrate the applicability of the theory.
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