Physical Chemistry Seminar: Professor Lukas Muechler, The Pennsylvania State University
About the Seminar
"Strong Correlations and Topological Transitions in Symmetry-Forbidden Chemical Reactions"
Classifying energy level connectivity via topological invariants has become a standard tool in condensed-matter physics. Despite many fundamental questions, extending these concepts to molecular systems has recently attracted significant interest. Reactions governed by orbital symmetry conservation are ideal candidates to test this extension, as they classify pathways as symmetry-allowed or symmetry-forbidden depending on whether molecular orbitals cross along the reaction coordinate. However, the presence of strong electronic correlations in these reactions invalidates the framework underlying topological band theory, preventing direct generalization. Here, we introduce a formalism in terms of Green's functions to classify orbital symmetry-controlled reactions even in the presence of strong electronic correlations. Focusing on prototypical 4pi electrocyclizations, we show that symmetry-forbidden pathways are characterized by crossings of Green's function zeros, in stark contrast to the crossings of poles as predicted by molecular-orbital theory. We introduce symmetry-resolved invariants that provide endpoint diagnostics for symmetry-preserving paths and motivate direct zero-tracking when symmetry is weakly broken. The result is a many-body generalization of orbital-crossing selection rules and a bridge to established concepts from topological and strong interaction physics in a molecular setting.
About the Speaker
Lukas Muechler is an Assistant Professor of Chemistry and Physics at Penn State University. As an undergrad, he worked with Claudia Felser at the University of Mainz and the Max Planck Institute for Chemical Physics of Solids. Lukas obtained his PhD from Princeton University in Chemistry working with Roberto Car. Before moving to Penn State, he was a Flatiron Research Fellow at the Center for Computational Quantum Physics of the Flatiron Institute in NYC. His research primarily addresses interdisciplinary challenges at the intersection of chemistry and physics, focusing on developing new theoretical tools and concepts for guiding material discovery and design. A focus of his group is to utilize recent breakthroughs in topological condensed matter physics to analyze chemical reactions and the properties of quantum materials. Lukas’ research is supported by a DOE Early Career Award.