Abstract
Combining density-functional theory and many-body approaches we investigate the origin of the ferroelectric phase generally observed in TMTTF-X organic crystals. We solve by means of mean-field theory and exact diagonalization a two-dimensional tight-biding model built from density-functional theory calculations and we show that short-range interactions stabilize a dimerized charge-ordered state in a wide range of parameters. Two different charge-ordering patterns are found; these correspond to those observed for and . In the former case, a lattice dimerization couples with the charge ordering, leading to a polarization. Due to the interplay between charge and magnetic ordering, such polarization appears to be magnetically driven, thus revealing TMTTF-PF as a multiferroic material.
- Received 27 March 2011
DOI:https://doi.org/10.1103/PhysRevB.85.205146
©2012 American Physical Society