We report on the results of angle-resolved photoemission experiments on a quasi-one-dimensional MX-chain compound [Ni(chxn)2Br]Br2 (chxn = 1R,2R-cyclohexanediamine), a one-dimensional Heisenberg system with S=1/2 and J∼3600 K, which shows a gigantic non-linear optical effect. A "band" having about 500 meV energy dispersion is found in the first half of the Brillouin zone (0≤kb/π<1/2), but disappears at kb/π∼1/2. Two dispersive features, expected from the spin-charge separation, as have been observed in other quasi-one-dimensional systems like Sr2CuO3, are not detected. These characteristic features are well reproduced by the d-p chain model calculations with a small charge-transfer energy Δ compared with that of one-dimensional Cu-O based compounds. We propose that this smaller Δ is the origin of the absence of clear spin- and charge-separation in the photoemission spectra and strong non-linear optical effect in [Ni(chxn)2Br]Br2.
@article{arxiv.cond-mat/0112154,
title = {Angle-resolved photoemission study of MX-chain compound [Ni(chxn)$_2$Br]Br$_2$},
author = {Shin-ichi Fujimori and Akihiro Ino and Testuo Okane and Atsushi Fujimori and Kozo Okada and Toshio Manabe and Masahiro Yamashita and Hideo Kishida and Hiroshi Okamoto},
journal= {arXiv preprint arXiv:cond-mat/0112154},
year = {2009}
}