Marginal Paramagnetic State of a One-Dimensional Half-Filled Alternating Chain in (TTM-TTP)AuI<sub><b>2</b></sub>
作者:Tadashi Kawamoto、Takehiko Mori、Takashi Yamamoto、Hiroyuki Tajima、Yohji Misaki、Kazuyoshi Tanaka
DOI:10.1143/jpsj.69.4066
日期:2000.12.15
(TTM-TTP)AuI2 (TTM-TTP: 2,5-bis[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetra-thiapentalene) has it dimerized structure along the donor stacking direction. and shows semiconducting behavior below room temperature. ESR, static magnetic susceptibility, and optical reflectance of this salt hare been measured to investigate the spin state and the electronic correlation. The ESR signal. has been observed from room temperature to 3 K, and the spin susceptibility shows paramagnetic behavior with a rapid decrease below 10 K. The static magnetic susceptibility is paramagnetic and has an anomaly around 10 K in agreement with the ESR result. The chain axis optical reflectance spectra show clear optical gap in the mid-infrared region. An: attempt is undertaken to analyze the optical spectrum by means of the one-dimensional dimerized Hubbard model, which suggests that the on-site Coulomb repulsion, U, is small and the spin polarization is located at the marginal paramagnetic boundary. These results indicate that this compound is not a band-insulator but the Mott insulator with a small spin gap.