Department of Chemistry Seminar - Doran Raccah

The Department of Chemistry presents: Doran Raccah

Title: Mesoscale quantum dynamics in molecular materials

Location: WEL 2.122

Refreshments served at 3:15pm

When a molecule absorbs light in a condensed-phase material, the ensuing photo physics and ultimate fate of that excitation depends on the mesoscale environment: the 10–100 nm structural landscape of neighbors, disorder, and packing. Over the last decade, new experimental probes have begun to image these dynamics in real space and real time. Computational tools, on the other hand, have not kept up. Traditional quantum chemistry algorithms cannot reach the relevant length scales, and band structure calculations cannot capture the heterogeneity that defines real materials.

I will describe a new class of algorithms that uses a simple physical insight about the extent of exciton delocalization to break through this impasse. Excitons in these systems spread across only a handful of molecules, and this locality enables a formally exact open quantum systems algorithm whose computational cost scales as O(1) — that is, for sufficiently large materials, the cost stops growing with system size. I will describe how this development has enabled a new class of simulations appropriate for mesoscale quantum dynamics to both understand excited state processes in molecular materials and their associated spectroscopic signatures.