Rotational $g$ factors and Lorentz forces of molecules and solids from density-functional perturbation theory
Abstract
Applied magnetic fields can couple to atomic displacements via generalized Lorentz forces, which are commonly expressed as gyromagnetic factors. We develop an efficient first-principles methodology based on density-functional perturbation theory to calculate this effect in both molecules and solids to linear order in the applied field. Our methodology is based on two linear-response quantities: the macroscopic polarization response to an atomic displacement (i.e., Born effective charge tensor), and the antisymmetric part of its first real-space moment (the symmetric part corresponding to the dynamical quadrupole tensor). The latter quantity is calculated via an analytical expansion of the current induced by a long-wavelength phonon perturbation, and compared to numerical derivatives of finite-wavevector calculations. We validate our methodology in finite systems by computing the gyromagnetic factor of several simple molecules, demonstrating excellent agreement with experiment and previous density-functional theory and quantum chemistry calculations. In addition, we demonstrate the utility of our method in extended systems by computing the energy splitting of the low-frequency transverse-optical phonon mode of cubic SrTiO in the presence of a magnetic field.
Keywords
Cite
@article{arxiv.2112.11946,
title = {Rotational $g$ factors and Lorentz forces of molecules and solids from density-functional perturbation theory},
author = {Asier Zabalo and Cyrus E. Dreyer and Massimiliano Stengel},
journal= {arXiv preprint arXiv:2112.11946},
year = {2022}
}