Variational Squeezed Davydov Ansatz for Realistic Chemical Systems with Nonlinear Vibronic Coupling

Chemical systems normally possess strong nonlinear vibronic couplings at both zero and finite temperature. For the operator into a variational coherent-state-based method, Davydov ansatz, to simulate the quantum dynamics and the respective spectroscopy. Two molecular systems, pyrazine and the 2-pyridone dimer, are taken as calculated model systems, both of which involve nontrivial quadratic vibronic couplings in high- and low-frequency regions, respectively. Upon a comparison with the benchmarks, the method manifests its advantage for nonlinear couplings. The squeezed bases are also proven to be applicable for the finite temperature by adapting with the thermofield dynamics.

Automated summary

Chemical systems typically exhibit strong nonlinear vibronic couplings at both zero and finite temperatures. The Davydov ansatz method, based on variational coherent states, is used to simulate quantum dynamics and spectroscopy. Two molecular systems, pyrazine and the 2-pyridone dimer, are studied as model systems, showing nontrivial quadratic vibronic couplings in different frequency regions. The method proves advantageous for nonlinear couplings, and squeezed bases are demonstrated to be applicable at finite temperatures using thermofield dynamics.