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Physics Colloquium Series: Nicholas P. Breznay
(Physics Lecture Series) Department of Physics, Harvey Mudd College
“Searching for new particles in quantum materials: the hunt for Kitaev magnons”
As physicists, we are always on the lookout for new particles and new interactions, from the high- energy frontier at the Large Hadron Collider to the “spooky action at a distance” that connects quantum-entangled particles. Crystalline solids – macroscopic materials constructed out of identical unit-cell building blocks – provide a fascinating laboratory for studying broken symmetries where searches for new particles and interactions often go hand-in-hand. Magnetic materials provide an excellent example of this intertwined process – in magnets, emergent particles known as “magnons” arise from the coupling between adjacent magnetic moments. In this talk, I will review a simple toy model – a chain of masses and springs – and use it to explore how dispersion relations reveal the existence of emergent particles in solid-state materials. Experimentally, we’ll hunt for the signatures of a new particle in lithium iridate (Li2IrO3), an unconventional magnetic material that exhibits frustration due to its novel Kitaev magnetic interaction. I will describe the strange magnetism in Li2IrO3, and recent experiments to study the magnetic properties of Li2IrO3 using resonant inelastic x-ray scattering (RIXS). Using this technique, our team recently measured the dispersion of magnetic excitations in the magnetically frustrated state of Li2IrO3 and observed the telltale signature of a new particle, the Kitaev magnon.