Observation of the Kohn Anomaly and the Peierls Transition in TTF-TCNQ by X-Ray Scattering

Abstract

Evidences of the Kohn anomaly and the Peierls transition in TTF-TCNQ were found by X-ray scattering experiments. The Kohn anomalies observed at T =293 K and 63 K give the Fermi wave number, k F , of the one-dimensional electron system as 2 k F = b * /(3.7±0.2), where b * is the reciprocal lattice vector. At 54 K, the one-dimensional ordering of the lattice deformation due to the Peierls transition was found along the b -axis with the period of b '=(3.7±0.2) b . At 27 K, the three-dimensional ordering was observed giving the new unit cell as a '=4 a , b '=3.7 b and c '= c .