In the recent years, many physicists have been enamored with how topology – the study of shapes that cannot be deformed into one another – can be characterized and harnessed in various physical systems. Since the synthesis of the first topological material HgTe a decade ago, the realm of topology has expanded to include experimentally accessible systems like acoustic, mechanical, photonic and electrical circuit metamaterials. In this talk, Dr. Lee shall begin by providing a broad overview of the state-of-the-art in contemporary topological metamaterials design, focusing on how their special protected topological modes can enhance useful phenomena like floppy modes and lasing. Next, he shall introduce the concept of topological electrical circuits, and show how their topological nature is manifested as very distinct RLC resonances. Beyond simulating known phases of matter, circuits can also host many new hitherto unobserved phases, such as those generated by gain/loss feedback mechanisms with no analogue in electronic materials. He shall conclude his talk by highlighting new conceptual links between these emergent non-equilibrium and non-Hermitian phases with mathematical topics like knot theory and complex analysis.
Dr. Ching Hua Lee received his PhD in theoretical condensed matter physics from Stanford University in 2015 under the guidance of Prof. Xiaoliang Qi. There, he researched on fractionalized topological phases and the entanglement properties of holographic condensed matter. He is now a scientist at the Institute of High Performance Computing in Singapore, as well as an adjunct assistant professor at the National University of Singapore. His current research topics include topological metamaterials/circuits, non-Hermitian physics, Floquet dynamics, nodal metals, strongly correlated fractionalized electrons, conformal field theory and complex networks. Dr. Lee is especially passionate about bringing abstract theoretical physics into everyday, potentially technologically useful settings.