CNO neutrinos and dark matter searches in the nEXO neutrinoless double beta experiment

nEXO is a proposed next-generation neutrinoless double beta decay search in the isotope 136Xe, designed to achieve a half-life sensitivity of >10^28 years at 90% confidence. The primary detector is a single-phase liquid xenon time projection chamber (TPC) with a fiducial mass of 3.2 tonnes of xenon, enriched to 90% in 136Xe. In this work, we explore the possibility of using the nEXO TPC to detect solar neutrinos using charged-current "inverse beta decay" reactions on 136Xe nuclei. Recent measurements of the daughter nucleus 136Cs have identified low-lying isomeric states with O(100)ns lifetimes that would be populated in such reactions, enabling these events to be tagged using the prompt xenon scintillation signals. Here we present an evaluation of the sensitivity of the nEXO experiment to these signals. We show that, with good timing resolution in the light readout system, nEXO could make a background-free measurement of the solar CNO neutrino flux with statistical uncertainties approaching 25%, search for the predicted core-temperature-induced shift in the 7Be neutrino line with unprecedented precision, and perform world-leading searches for so-called "fermionic" dark matter interacting through charged-current-like reactions.