title: Multiferroicity in TTF-CA organic molecular crystals predicted through ab initio calculations.
abstract: We show by means of ab initio calculations that the organic molecular crystal TTF-CA is multiferroic: it has an instability to develop spontaneously both ferroelectric and magnetic ordering. Ferroelectricity is driven by a Peierls transition of the TTF-CA in its ionic state. Subsequent antiferromagnetic ordering strongly enhances the opposing electronic contribution to the polarization. It is so large that it switches the direction of the total ferroelectric moment. Within an extended Hubbard model, we capture the essence of the electronic interactions in TTF-CA, confirm the presence of a multiferroic groundstate, and clarify how this state develops microscopically.
authors.affiliation: Consiglio Nazionale delle Ricerche-Istituto Nazionale per la Fisica della Materia (CNR-INFM), CASTI Regional Laboratory, 67100 L'Aquila, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Giovannetti
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Kumar
authors.forename: Alessandro
authors.initials: A
authors.lastname: Stroppa
authors.forename: Jeroen
authors.initials: J
authors.lastname: van den Brink
authors.forename: Silvia
authors.initials: S
authors.lastname: Picozzi