Search for MeV Electron Recoils from Dark Matter in EXO-200

We present a search for electron-recoil signatures from the charged-current absorption of fermionic dark matter using the EXO-200 detector. We report an average electron recoil background rate of $6.8\times {10}^{-4}\mathrm{c}\mathrm{t}\mathrm{s}{\mathrm{k}\mathrm{g}}^{-1}{\mathrm{y}\mathrm{r}}^{-1}{\mathrm{k}\mathrm{e}\mathrm{V}}^{-1}$ above $4\mathrm{M}\mathrm{e}\mathrm{V}$ and find no statistically significant excess over our background projection. Using a total ${}^{136}\mathrm{X}\mathrm{e}$ exposure of $234.1\mathrm{k}\mathrm{g}\mathrm{y}\mathrm{r}$ we exclude new parameter space for the charged-current absorption cross-section for dark matter masses between $m_{\chi }=2.6\mathrm{M}\mathrm{e}\mathrm{V}-11.6\mathrm{M}\mathrm{e}\mathrm{V}$ with a minimum of $6\times {10}^{-51}{\mathrm{c}\mathrm{m}}^2$ at $8.3\mathrm{M}\mathrm{e}\mathrm{V}$ at the $90\mathrm{\%}$ confidence level.