Enhancement of nuclear spin-spin interactions by collective electronic modes*

Nuclear magnetic resonance (NMR) has been used to great success as an indirect probe of electronic behavior, as changes in the electronic phase can shift or broaden resonance signals. We propose how electronic phases can also introduce feedback loops to nuclear spin behavior. Under strong spin-spin interactions, nuclear ensembles will exhibit nonlinear dynamics and give complicated responses to standard pulse protocols. Enhancement mechanisms of the double-exchange interaction between electrons and nuclei due to the presence of many-body collective modes will be explored, along with implications for observing these non-classical electronic states in NMR experiments.