Deciphering the fundamental charge excitations of quantum materials through numerical simulation

Advances in experimental spectroscopy continually unveil novel excitations in quantum materials. Identifying and modeling these excitations are crucial to understanding their role in emergent material properties. In this talk, I will highlight three cases where numerical simulations were instrumental in resolving the nature of collective charge excitations observed in spectroscopy. First, I will discuss the discovery of interlayer acoustic plasmons in a high-temperature cuprate superconductor, revealed through resonant inelastic X-ray scattering (RIXS) and quantum Monte Carlo simulations. Next, I will present the identification of Pines’ demon—an interband acoustic plasmon—in Sr₂RuO₄, where band-resolved random phase approximation (RPA) calculations were essential in confirming its neutral, interband nature. Finally, I will introduce our preliminary RIXS study on MgB₂, which, supported by detailed polarizability calculations, suggests the first direct observation of the Lindhard continuum. In each case, numerical simulations not only clarified the fundamental nature of these excitations but also provided key insights into the material properties and experimental conditions that enabled their detection.

Bio: Edwin Huang is currently an Assistant Professor of Physics and Astronomy at the University of Notre Dame. Prior to joining Notre Dame, he was a Gordon and Betty Moore Postdoctoral Fellow at the University of Illinois, Urbana-Champaign. He received his PhD from Stanford University in the field of computational condensed matter theory. His research involves utilizing a combination of large-scale numerical and analytical techniques to study the emergent properties of strongly correlated quantum materials through model calculations and comparisons against experimental spectroscopy.