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arXiv · 2410.18838

Phaseless auxiliary-field quantum Monte Carlo method for cavity-QED matter systems

Lukas Weber·Leonardo dos Anjos Cunha·Miguel A. Morales·Angel Rubio·Shiwei Zhang
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Abstract

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.

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Lukas Weber, Leonardo dos Anjos Cunha, Miguel A. Morales, Angel Rubio, Shiwei Zhang. 2024-10-24. Phaseless auxiliary-field quantum Monte Carlo method for cavity-QED matter systems. https://doi.org/10.1021/acs.jctc.4c01459

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