# Dynamic multipolar polarizabilities and hyperpolarizabilities of the Sr lattice clock

## TL;DR

This paper develops a combined theoretical approach to accurately calculate the dynamic multipolar polarizabilities and hyperpolarizabilities of strontium atoms at the magic wavelength, crucial for improving optical lattice clock precision.

## Contribution

It introduces a combined Dirac-Fock plus core polarization and relativistic configuration interaction method for precise calculations of atomic properties relevant to optical clocks.

## Key findings

- Calculated differential hyperpolarizability is consistent with existing theory and experiments.
- Differential multipolar polarizability validates some previous theoretical work.
- Results differ from recent experimental measurements, highlighting ongoing uncertainties.

## Abstract

The progress in optical clock with uncertainty at a level of $10^{-18}$ requires unprecedented precision in estimating the contribution of multipolar and higher-order effects of atom-field interactions. Current theoretical and experimental results of dynamic multipolar polarizabilities and hyperpolarizabilities at the magic wavelength for the Sr clock differ substantially. We develop a combined approach of the Dirac-Fock plus core polarization (DFCP) and relativistic configuration interaction (RCI) methods to calculate dynamic multipolar polarizabilities and hyperpolarizabilities of the Sr atom. Our differential dynamic hyperpolarizability at the magic wavelength is $-2.09(43)\times10^{7}$ a.u., which is consistent with the existing theoretical and experimental results. Our differential multipolar polarizability is $2.68(94)\times 10^{-5}$ a.u., which validates independently the theoretical work of Porsev {\em et al.} [Phys. Rev. Lett. 120, 063204 (2018)], but different from recent measurement of Ushijima {\em et al.} [Phys. Rev. Lett. 121, 263202 (2018)].