Theses Doctoral

Infrared Nanoscopy of Anisotropic and Correlated Quantum Materials

Ruta, Francesco Luigi

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.

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More About This Work

Academic Units
Applied Physics and Applied Mathematics
Thesis Advisors
Basov, Dmitri N.
Degree
Ph.D., Columbia University
Published Here
November 6, 2024