title: Electronic Structure of the Kitaev Material α-RuCl3Probed by Photoemission and Inverse Photoemission Spectroscopies.
abstract: Recently, α-RuCl3has attracted much attention as a possible material to realize the honeycomb Kitaev model of a quantum-spin-liquid state. Although the magnetic properties of α-RuCl3have been extensively studied, its electronic structure, which is strongly related to its Kitaev physics, is poorly understood. Here, the electronic structure of α-RuCl3was investigated by photoemission (PE) and inverse-photoemission (IPE) spectroscopies. The band gap was directly measured from the PE and IPE spectra and was found to be 1.9 eV, much larger than previously estimated values. Local density approximation (LDA) calculations showed that the on-site Coulomb interaction U could open the band gap without spin-orbit coupling (SOC). However, the SOC should also be incorporated to reproduce the proper gap size, indicating that the interplay between U and SOC plays an essential role. Several features of the PE and IPE spectra could not be explained by the results of LDA calculations. To explain such discrepancies, we performed configuration-interaction calculations for a RuCl63-cluster. The experimental data and calculations demonstrated that the 4d compound α-RuCl3is a Jeff= 1/2 Mott insulator rather than a quasimolecular-orbital insulator. Our study also provides important physical parameters required for verifying the proposed Kitaev physics in α-RuCl3.
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.|Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea.
authors.forename: Soobin
authors.initials: S
authors.lastname: Sinn
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.|Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea.
authors.forename: Choong Hyun
authors.initials: CH
authors.lastname: Kim
authors.affiliation: Computational Condensed Matter Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.|Interdisciplinary Theoretical Science (iTHES) Research Group, RIKEN, Wako, Saitama 351-0198, Japan.
authors.forename: Beom Hyun
authors.initials: BH
authors.lastname: Kim
authors.affiliation: Department of Physics, Inha University, Incheon 22212, Republic of Korea.
authors.forename: Kyung Dong
authors.initials: KD
authors.lastname: Lee
authors.affiliation: Department of Physics, Inha University, Incheon 22212, Republic of Korea.
authors.forename: Choong Jae
authors.initials: CJ
authors.lastname: Won
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.|Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea.
authors.forename: Ji Seop
authors.initials: JS
authors.lastname: Oh
authors.affiliation: Department of Physics, University of Seoul, Seoul 02504, Republic of Korea.
authors.forename: Moonsup
authors.initials: M
authors.lastname: Han
authors.affiliation: Department of Physics, University of Seoul, Seoul 02504, Republic of Korea.
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Chang
authors.affiliation: Department of Physics, Inha University, Incheon 22212, Republic of Korea.
authors.forename: Namjung
authors.initials: N
authors.lastname: Hur
authors.affiliation: Hiroshima Synchrotron Radiation Center, Hiroshima University, Kagamiyama 2-313, Higashi-Hiroshima 739-0046, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sato
authors.affiliation: Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.
authors.forename: Byeong-Gyu
authors.initials: BG
authors.lastname: Park
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.|Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea.
authors.forename: Changyoung
authors.initials: C
authors.lastname: Kim
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.|Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea.
authors.forename: Hyeong-Do
authors.initials: HD
authors.lastname: Kim
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.|Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea.
authors.forename: Tae Won
authors.initials: TW
authors.lastname: Noh