Anisotropic polarizability of erbium atoms

TL;DR

This paper measures and analyzes the anisotropic polarizability of ultracold erbium atoms, revealing how it depends on angle and state, with implications for spin manipulation in optical traps.

Contribution

It provides the first combined experimental and theoretical analysis of erbium's anisotropic polarizability, including angle dependence and state-specific effects.

Findings

Polarizability depends on the angle between laser polarization and magnetic field.

Good agreement between experimental measurements and theoretical calculations.

Anisotropic tensor polarizability can be exploited for spin-selective control.

Abstract

We report on the determination of the dynamical polarizability of ultracold erbium atoms in the ground and in one excited state at three different wavelengths, which are particularly relevant for optical trapping. Our study combines experimental measurements of the light shift and theoretical calculations. In particular, our experimental approach allows us to isolate the different contributions to the polarizability, namely the isotropic scalar and anisotropic tensor part. For the latter contribution, we observe a clear dependence of the atomic polarizability on the angle between the laser-field-polarization axis and the quantization axis, set by the external magnetic field. Such an angle-dependence is particularly pronounced in the excited-state polarizability. We compare our experimental findings with the theoretical values, based on semi-empirical electronic-structure calculations and we observe a very good overall agreement. Our results pave the way to exploit the anisotropy of the tensor polarizability for spin-selective preparation and manipulation.