Charge radii of calcium isotopes within relativistic density functional theory: The finite size of the nucleon and quadrupole shape-fluctuation effects

The anomaly in the charge radii of Ca isotopes has been puzzling for nuclear theory for decades. We present the first self-consistent solution to this puzzle within the density functional theory without resorting to local parameter adjustment. By taking into account both the intrinsic electromagnetic structure of nucleons and the zero-point motions of nuclear shape, which have been often neglected in previous studies, the similar charge radii of $^{40}\mathrm{Ca}$ and $^{48}\mathrm{Ca}$, as well as an inverted parabolic behavior between them, are reproduced. It is found that these effects also play crucial roles in the description of the isotonic shift between the charge radii of Sn and Cd isotopes.