CCB Seminar: Xavier Roy (Columbia)

"Quantum complexity in simple materials"

Two-dimensional (2D) materials have received widespread attention over the past 20 years due to their remarkable physical, mechanical and chemical properties, and our ability to integrate them into devices. In this seminar, I will discuss a new approach for realizing long-sought electronic structures of geometrically frustrated lattice models (e.g. kagome and pyrochlore), by “decorating” un-frustrated, primitive lattices with a particular set of atomic orbitals. In the process, we identify the vdW intermetallic compound Pd5AlI2 as the first material to realize the electronic structure of the 2D Lieb lattice – featuring Dirac-like bands intersected by a flat band – persisting in ambient conditions down to the monolayer limit. I will discuss how this unique electronic structure gives rise to compact localized states and bound states in continuum (BICs), which could provide a platform for lossless and topologically protected electronic processes. I will then detail our recent development of a new class of 2D materials called single-ion quantum multiferroics, which combine polar order and quantum magnetism.