セミナー情報

原子力機構・兵県大合同物性コロキウム(第70回)

日時: 平成22年8月5日(木) 14:00〜
Date and time: 5th Aug. (Thu.) 14:00〜
場所: SPring-8, 萌光館
Place: SPring-8, "HOUKOUKAN" seminar room
Title: Spin frustration and Charge ordering in TMTTF salts
講演者: 吉見一慶 (産総研)
Speaker: Kazuyoshi Yoshimi (AIST)
Abstract:

Quasi-one-dimensional organic conductors (TMTTF)2X salts exhibit various types of phase transitions such as magnetic ordering, charge ordering (CO), and superconducting transitions [1]. Among them, (TMTTF)2SbF6 shows a peculiar behavior under pressure: a cooperative reduction of CO and anti-ferromagnetic phase transition temperatures by the application of pressure has been reported by NMR measurements [2]. This result naively does not coincide with the case for typical CO transitions, where CO suppresses the tendency toward magnetic ordering due to decrease of the effective spin exchange coupling [3]. To explain this behavior, we investigate a 1/4-filled quasi-one-dimensional extended Hubbard model with inter-chain hopping and Coulomb interactions. In our model, the diagonal inter-chain hopping causes spin frustration between the dimers on the one-dimensional chains. By numerical exact diagonalization method, we calculate the charge and spin structure factors and investigate the relation between charge-ordering and inter-chain hopping. To compare the results with experiments, we determine the hopping parameters by first principles band calculation for several TMTTF salts and discuss the relation between spin frustration and CO.

[1] S. E. Brown, P. M. Chaikin, and M. J. Naughton, in “The Physics of Organic Superconductors and Conductors”, Ed. A. Lebed, Springer (2008)
[2] W. Yu et al., Phys. Rev. B. 70 (2004) 121101.
[3] Y. Tanaka and M. Ogata, J. Phys. Soc. Jpn. 74 (2005) 3283.