PNNL

The Science   

The notion of photonic reagents, shaped light fields that work in concert with molecular degrees of freedom to control chemical reactivity, has captivated the imagination of scientists. Polaritonic chemistry represents an exciting reimagining of this goal, where nanoscale optical cavities are used to entrap molecules and photons to dramatically enhance their interactions. Despite recent developments in ab initio polaritonic methods for simulating polaritonic chemistry under electronic strong coupling, their capabilities are limited, especially in cases where the molecule also features strong electronic correlation. To bridge this gap, a team of researchers from the J. Heyrovský Institute of Physical Chemistry in the Czech Republic, Academy of Sciences of the Czech Republic, University of North Carolina-Charlotte, and Pacific Northwest National Laboratory developed a new theoretical method called Quantum Electrodynamics Density Matrix Renormalization Group (QED-DMRG) by extending the powerful DMRG method that has been widely used to study strongly correlated systems.

The Impact

Light, when nanoconfined in cavities and made to interact strongly with molecules, can result in new ways to control chemical reactions and create new quantum states. The new QED-DMRG method opens the door to studying more complex and strongly correlated molecular systems in cavity environments.

Summary

Polaritonic chemistry explores how light-matter interactions influence the behavior of molecules. Despite recent developments in ab initio methods for simulating polaritonic chemistry under electronic strong coupling, strongly correlated molecular cases are still challenging to simulate. To address this gap, the team developed a novel method by combining cavity quantum electrodynamics with the DMRG algorithm. This approach incorporates a robust parallel implementation of DMRG that provides efficient controlled approximations to the numerically exact solutions, resulting in massive computational cost savings. 

The team used this approach to investigate a complex, strongly correlated system. They applied the QED-DMRG algorithm to study the cavity effects on the singlet excitations of n-oligoacenes, a class of organic molecules with 2-5 aromatic rings used for photovoltaic applications. Their findings indicate that the influence of the cavity intensifies almost linearly with larger acenes, highlighting the influence of molecular structure on polaritonic behavior. These studies reveal potential avenues for tuning the properties of polycyclic aromatic molecules through molecular design for specified applications. 

Contact

Niri Govind 
Pacific Northwest National Laboratory 
niri.govind@pnnl.gov

Funding

This work was supported by the Center for Many-Body Methods, Spectroscopies, and Dynamics for Molecular Polaritonic Systems (MAPOL) under FWP 79715, which is funded at Pacific Northwest National Laboratory (PNNL) as part of the Computational Chemical Sciences (CCS) program by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences.