Phaseless Auxiliary-Field Quantum Monte Carlo Method for Cavity-QED Matter Systems

• DOI: 10.1021/acs.jctc.4c01459
• Publication Date: 2025-01-17T17:23:31Z
• Authors: Lukas Weber; Leonardo dos Anjo...; Miguel A. Morales; Angel Rubio; Shiwei Zhang
• Keywords: Chemical Physics (physics.chem-ph); Physics - Chemical Physics; FOS: Physical sciences

We present a generalization of the phaseless auxiliary-field quantum Monte Carlo (AFQMC) method to cavity quantum-electrodynamical (QED) matter systems. The method can be formulated in both the Coulomb and the dipole gauge. We verify its accuracy by benchmarking calculations on a set of small molecules against full configuration interaction and state-of-the-art QED coupled cluster (QED-CCSD) calculations. Our results show that (i) gauge invariance can be achieved within correlation-consistent Gaussian basis sets, (ii) the accuracy of QED-CCSD can be enhanced significantly by adding the standard perturbative triples correction without light-matter coupling, and (iii) there is a straightforward way to evaluate the differential expression for the photon occupation number that works in any gauge. The high accuracy and favorable computational scaling of our AFQMC approach will enable a broad range of applications. Besides polaritonic chemistry, the method opens a way to simulate extended QED matter systems.<br/>10 pages, 7 figures, v2: published version<br/>