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Condensed Matter Seminar: "Spectroscopic investigations of quantum criticality, domain structures, and spin-orbit coupling"
My research program is directed at developing a fundamental understanding of the mechanisms underlying the interplay between charge, structure, magnetism, and orbitals in complex materials. This insight facilitates the development of tunable multifunctional solids and nanomaterials, which are scientifically and technologically important. Our main strategy involves investigating the dynamic response of functional materials such as multiferroics and frustrated systems under external stimuli such as high magnetic fields, under unusual chemical and photochemical activation, and at very small sizes where quantum confinement becomes apparent. This allows us to learn about the relationships between different ordered and emergent states, explore the dynamic aspects of coupling, and gain insight into the generality of these phenomena and their underlying mechanisms. As examples, I will discuss (i) the use of high magnetic fields to drive a quantum critical transition in Mn[N(CN)2]2 to reveal amplified magnetoelastic coupling, (ii) the spectroscopic signatures of vortex and stripe domain structure in hexagonal ErMnO3 and their impact on polarization, and (iii) the discovery of the Burstein-Moss effect in Re-substituted MoS2 nanoparticles – which quantifies the relationship between dopant concentration and carrier density. In addition to broadening the understanding of novel solids under extreme conditions, multifunctional materials and their assemblies are of interest for light harvesting, electronic, spintronic, and solid state lubrication applications.
Left: Schematic view of the Burstein-Moss effect in electron doped MoS2 nanoparticles.
Right: Measured blue-shift of exciton B as a function of Re substitution compared with predictions of the model. This agreement establishes a quantitative connection between actual dopant concentration and carrier density for nanoscale metal dichalcogenides.