Polaritonic Chemistry using the Density Matrix Renormalization Group Method

TL;DR

This paper introduces a novel DMRG-based method for simulating polaritonic chemistry under strong coupling, effectively handling electronic correlation and photonic degrees of freedom with improved computational efficiency.

Contribution

The authors develop a DMRG approach for cavity QED calculations that overcomes limitations of existing methods, especially for strongly correlated molecules in polaritonic chemistry.

Findings

Cavity effects increase with larger acenes.

DMRG efficiently manages photonic degrees of freedom.

Computational cost remains constant with increasing photonic basis.

Abstract

The emerging field of polaritonic chemistry explores the behavior of molecules under strong coupling with cavity modes. 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, we have developed a novel method for cavity QED calculations utilizing the Density Matrix Renormalization Group (DMRG) algorithm in conjunction with the Pauli-Fierz Hamiltonian. Our approach is applied to investigate the effect of the cavity on the S0 -S1 transition of n-oligoacenes, with n ranging from 2 to 5, encompassing 22 fully correlated {\pi} orbitals in the largest pentacene molecule. Our findings indicate that the influence of the cavity intensifies with larger acenes. Additionally, we demonstrate that, unlike the full determinantal representation, DMRG efficiently optimizes and eliminates excess photonic degrees of freedom, resulting in an asymptotically constant computational cost as the photonic basis increases.