Precision spectroscopy of ytterbium ions for tests of fundamental physics
Creators: name: Yeh, Chih-Han
Publisher: name: Hannover : Institutionelles Repositorium der Leibniz Universität Hannover
Year: 2024
Subjects: subject: local Lorentz-invariance
subject: Standard Model Extension
subject: isotope-shift measurement
subject: fifth force
subject: King-plot analysis
subject: multi-ion interrogation
subject: lokale Lorentz-Invarianz
subject: Erweiterung des Standardmodells
subject: Isotopenverschiebungsmessung
subject: fünfte Kraft
subject: King-Plot-Analyse
subject: Multi-Ionen-Abfrage
subject: Dewey Decimal Classification::500 | Naturwissenschaften::530 | Physik

description: Trapped-ion quantum sensors have become sensitive tools for the search of physics beyond the Standard Model. In this thesis, a measurement on the test of local Lorentz-invariance with a single ytterbium (Yb) ion and the search of new bosons coupling the neutrons and the electrons via the isotope-shift measurements are presented. In the attempt to unify all fundamental forces at the Planck scale, it is suggested that breaking of Lorentz symmetry would occur. In the framework of Standard Model Extension, such violation would lead to energy shifts of atomic states with non-spherical electron orbitals. With high-precision spectroscopy of such states in a Michelson-Morley-type experiment, we search for violation of LLI. Two composite radio-frequency pulse sequences have been investigated and the optimal one is used in the LLI test to fully benefit from the high susceptibility of the $^{2}F_{7/2}$ state in $^{172}\mathrm{Yb}^{+}$. With this method, we constrained the symmetry-breaking coefficients at the $10^{-21}$ level, which represent the most stringent test of this kind of violation in the combined electron-photon sector. Theoretical proposals suggest a new boson coupling the neutrons and electrons in an atom, presented as a fifth force. This coupling would lead to a small shift in energy levels which can be probed with isotope-shift measurements. King-plot analysis uses these measurements and provides a way of distinguishing between the leading SM behavior and higher-order effects without relying on atomic structure calculations. A deviation from the linearity of the King plot would hint towards undetermined higher-order effects from the SM (e.g. field shift and mass shift) or even physics beyond the SM. To investigate and provide a deeper understanding of the seen nonlinearity in Yb. From that, isotope shifts at the $10^{-8}$ to the $10^{-9}$ level were determined. We also collaborated with Klaus Blaum's group at the Max Planck Institute for Nuclear Physics in Heidelberg where they measured mass ratios to the $10^{-12}$ level. With these precise data and considering the leading SM nonlinearity, we extract a world-leading King-plot bound on the mass and the interaction energy of this new boson that mediates the fifth force. For future improvements of the LLI test and the isotope-shift measurements, the interrogation of multiple ions in an ion chain has been investigated and promising results have been observed. The leading systematic effects are also discussed to further improve the accuracy of the determination of isotope shifts.