title: Separation between low-energy hole dynamics and spin dynamics in a frustrated magnet.
abstract: An angle-resolved photoemission spectroscopy (ARPES) study is reported on a Mott insulator NiGa2S4 in which Ni2+ (S=1) ions form a triangular lattice and the Ni spins do not order even in its ground state. The first ARPES study on the two-dimensional spin-disordered system shows that low-energy hole dynamics at high temperatures is characterized by wave vectors Q(E) which are different from wave vectors Q(M) dominating low-energy spin excitations at low temperatures. The unexpected difference between Q(E) and Q(M) is deeply related to charge fluctuation across the Mott gap in the frustrated lattice and is a key issue to understand the spin-disordered ground states in Mott insulators.
authors.affiliation: Department of Physics, University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8561, Japan.
authors.forename: Kou
authors.initials: K
authors.lastname: Takubo
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nambu
authors.forename: Satoru
authors.initials: S
authors.lastname: Nakatsuji
authors.forename: Yuki
authors.initials: Y
authors.lastname: Wakisaka
authors.forename: Takaaki
authors.initials: T
authors.lastname: Sudayama
authors.forename: David
authors.initials: D
authors.lastname: Fournier
authors.forename: Giorgio
authors.initials: G
authors.lastname: Levy
authors.forename: Andrea
authors.initials: A
authors.lastname: Damascelli
authors.forename: Masashi
authors.initials: M
authors.lastname: Arita
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Namatame
authors.forename: Masaki
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizokawa