title: Evolution of ferroelectricity in tetrathiafulvalene-p-chloranil as a function of pressure and temperature.
abstract: The neutral-to-ionic phase transition in the mixed-stack charge-transfer complex tetrathiafulvalene-p-chloranil (TTF-CA) has been studied by pressure-dependent infrared spectroscopy up to p = 11 kbar and down to low temperatures, T = 10 K. By tracking the C=O antisymmetric stretching mode of CA molecules, we accurately determine the ionicity of TTF-CA in the pressure-temperature phase diagram. At any point, the TTF-CA crystal bears only a single ionicity; there is no coexistence region or an exotic high-pressure phase. Our findings shed new light on the role of electron-phonon interaction in the neutral-ionic transition.
authors.affiliation: 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Dengl
authors.affiliation: 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Beyer
authors.affiliation: 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Peterseim
authors.affiliation: 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
authors.forename: Tomislav
authors.initials: T
authors.lastname: Ivek
authors.affiliation: 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Untereiner
authors.affiliation: 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Dressel