Abstract
Ultra-precise optical atomic clocks show promise as the next-generation frequency standard, as well as
quantum sensors for exploring new physics beyond the standard model. This article reviews our attempts
to search for new physics through precise spectroscopy of neutral ytterbium atoms. Neutral ytterbium
atoms have multiple clock transitions and many stable isotopes, making them suitable for the search for
new physics. By measuring the isotope shift of the 1S0 − 3P0 transition at the Hz level, we can observe the
nonlinearity of the generalized King’s plot. Additionally, a new clock transition from the ground state to
the metastable 4f 135d6s2 (J = 2) state, which was theoretically predicted, is directly observed, and investigations
are carried out on its isotope shift, g factor, hyperfine structure, magic wavelength, and trap
lifetime. These achievements open up the possibility of future new physics searches.
