Development of Proton-Electron-Coupled Organic Crystals

Abstract

The highly “electron-electron” correlated researches have been vigorously developed in π-, d-, and f-electron systems. Moreover, “electron-proton” coupled studies have attracted much attentions in π-electron based organic crystals. In this review, the basic model, room-temperature ferroelectricity, and novel phenomena of conductivities and magnetism by electron-proton coupling in organic crystals were introduced. Especially, the π-electron based quantum spin liquid state coupled with quantum fluctuation of protons in hydrogen bonds and the switching of conductivity and magnetism triggered by the disorder-order transition of deuterium in hydrogen-bonds have been reported as novel proton-electron coupling properties. Moreover, these phenomena with dynamical π-electron-proton coupling can be controlled by external stimuli such as pressure and electric field.