Adiabatic perturbation theory for two-component systems with one heavy component

Ryan Requist*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Perturbation theory with respect to the kinetic energy of the heavy component of a two-component quantum system is introduced. An effective Hamiltonian that is accurate to second order in the inverse heavy mass is derived. It contains a new form of kinetic energy operator with a Hermitian mass tensor and a complex-valued vector potential. All of the potentials in the effective Hamiltonian can be expressed in terms of covariant derivatives and a resolvent operator. The most salient application of the theory is to systems of electrons and nuclei. The accuracy of the theory is verified numerically in a model diatomic molecule and analytically in a vibronic coupling model.

Original languageEnglish
Article number024311
JournalPhysical Review B
Volume111
Issue number2
DOIs
StatePublished - 1 Jan 2025

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© 2025 American Physical Society.

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