Consiglio Nazionale delle Ricerche-Istituto Nazionale per la Fisica della Materia (CNR-INFM), CASTI Regional Laboratory, 67100 L'Aquila, Italy.
Phys Rev Lett. 2009 Dec 31;103(26):266401. doi: 10.1103/PhysRevLett.103.266401. Epub 2009 Dec 28.
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.
我们通过从头算的方法证明有机分子晶体 TTF-CA 是多铁性的：它具有自发发展铁电和磁有序的不稳定性。铁电性是由 TTF-CA 在离子态下的 Peierls 跃迁驱动的。随后的反铁磁有序强烈增强了极化的相反电子贡献。这种贡献非常大，以至于它改变了总铁电极化矩的方向。在扩展的 Hubbard 模型中，我们捕捉到了 TTF-CA 中电子相互作用的本质，证实了多铁基态的存在，并阐明了这种状态如何在微观上发展。
