Unraveling the polar state in TMTTF2-PF6 organic crystals

Gianluca Giovannetti, Sanjeev Kumar, Jean-Paul Pouget, and Massimo Capone
Phys. Rev. B 85, 205146 – Published 29 May 2012

Abstract

Combining density-functional theory and many-body approaches we investigate the origin of the ferroelectric phase generally observed in TMTTF2-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 X=PF6 and X=SCN. 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 TMTTF2-PF6 as a multiferroic material.

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  • Received 27 March 2011

DOI:https://doi.org/10.1103/PhysRevB.85.205146

©2012 American Physical Society

Authors & Affiliations

Gianluca Giovannetti1, Sanjeev Kumar2, Jean-Paul Pouget3, and Massimo Capone1,4

  • 1Democritos National Simulation Center, Consiglio Nazionale delle Ricerche, Istituto Officina dei Materiali (IOM) and Scuola Internazionale Superiore di Studi Avanzati (SISSA), Via Bonomea 265, 34136 Trieste, Italy
  • 2Indian Institute of Science Education and Research (IISER) Mohali, SAS Nagar, Sector 81, Mohali 140306, India
  • 3Laboratoire de Physique des Solides, Université Paris Sud, CNRS, UMR 8502, 91405 Orsay, France
  • 4Physics Department, University “Sapienza,” Piazzale A. Moro 2, 00185 Rome, Italy

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Issue

Vol. 85, Iss. 20 — 15 May 2012

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