Angle-resolved photoemission study of the -chain compound [Ni(chxn)Br]Br; Spin-charge separation in hybridized - chains

Fujimori, Shinichi   ; Ino, Akihiro; Okane, Tetsuo  ; Fujimori, Atsushi; Okada, Kozo*; Manabe, Toshio*; Yamashita, Masahiro*; Kishida, Hideo*; Okamoto, Hiroshi*

We report on the results of angle-resolved photoemission experiments on a quasi-one-dimensional -chain compound [Ni(chxn)Br]Br (chxn = 1,2-cyclohexanediamine), a one-dimensional Heisenberg system with and K, which shows a gigantic non-linear optical effect. A "band" having about 500meV energy dispersion is found in the first half of the Brillouin zone , but disappears at . Two dispersive features, expected from the spin-charge separation, as have been observed in other quasi-one-dimensional systems like SrCuO, are not detected. These characteristic features are well reproduced by the - chain model calculations with a small charge-transfer energy compared with that of one-dimensional Cu-O based compounds. We propose that this smaller is the origin of the absence of clear spin- and charge-seperation in the photoemission spectra and strong non-linear optical effect in [Ni(chxn)Br]Br.