Direct Detection Constraints on Dark Photons with the CDEX-10 Experiment at the China Jinping Underground Laboratory

We report constraints on the dark photon effective kinetic mixing parameter ($\kappa $) with data taken from two $p$-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on $\kappa $ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (${m}_{V}$) from 10 to $300\text{}\text{}\mathrm{eV}/{c}^{2}$ in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with ${m}_{V}$ from 0.1 to $4.0\text{}\text{}\mathrm{keV}/{c}^{2}$ are set from 449.6 kg-day data, with a minimum of $\kappa =1.3×{10}^{-15}$ at ${m}_{V}=200\text{}\text{}\mathrm{eV}/{c}^{2}$.