Collective phenomena can give quantum materials unusual properties not found in common materials. Electronic correlations are responsible for intriguing emergent effects like superconductivity, metal-to-insulator transitions, magnetism, etc. Also, anisotropic excitations of polar quantum matter can lead to hyperbolicity, when one crystal axis is metallic and another dielectric. Polaritons, half-light half-matter quasiparticles, have exotic properties in hyperbolic media and are influenced by electronic correlations.
In this dissertation, we use infrared near-field optical nanoscopy to interrogate various quantum materials both with strong anisotropy and electronic correlations and study their interplay and tunability. We first understand how near-field microscopes read out optical anisotropy and use our theory to study the metal-to-insulator transition in polycrystalline VO₂. Next, we demonstrate extreme tunability of hyperbolic phonon polaritons in α-MoO₃ by interfacing graphene. Finally, we introduce two novel hyperbolic systems: CrSBr and MoOCl₂, which host magnetically-enhanced hyperbolic exciton polaritons and ultra-low-loss hyperbolic plasmon polaritons, respectively.
| Identifer | oai:union.ndltd.org:columbia.edu/oai:academiccommons.columbia.edu:10.7916/brrx-bn61 |
| Date | January 2024 |
| Creators | Ruta, Francesco Luigi |
| Source Sets | Columbia University |
| Language | English |
| Detected Language | English |
| Type | Theses |
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