Negative Charge Transfer and Reduced on-site Coulomb Energy in Layered Topological Metals

ORAL

Abstract

The layered 3d transition-metal dichalcogenides CoTe2 and NiTe2 are known to be Dirac semi-metals. We study the electronic structure of CoTe2 to quantify the electronic structure parameters and compare it with the strongly correlated oxide CoO. Using Co L-edge 2p-3d resonant valence band photoemission spectroscopy(PES), we determine the Co on-site Coulomb energy (Udd) to be Udd = 3.0 eV for CoTe2, from measurements of the single particle 3d partial density of states and the two-hole correlation satellite. Charge transfer(CT) cluster model calculations of core level spectra validate the Udd value and also provide the charge transfer energy(Δ) between metal d-ligand p-states, and the d-p hybridization strength(Teg). It is found that CoTe2 is a negative charge-transfer material with Δ = -2.0 eV. In comparison, CoO is confirmed to be positive charge transfer insulator with Udd = 5.0 eV and Δ = 4.0 eV.  The d-p hybridization strength Teg for CoTe2 < CoO, and indicates that the reduced Udd in CoTe2 is not due to Teg. Similarly we obtain a negative Δ and reduced Udd in NiTe2 compared to NiO. However, in-spite of the reduced Udd values, CoTe2 and NiTe2 become topological metals only because Udd > |Δ| with p-p type lowest energy excitations which facilitate the formation of Dirac bands.

References

1. A. Chakraborty et. al. PRB 107, 085406 (2023).

2. B. Ghosh et. al. PRB 100, 195134 (2019).

3. A. R. Shelke et. al. PRL (submitted)

4. A. R. Shelke et. al. PRB (submitted)

*This work was supported by the National Science and Technology Council(NSTC) of Taiwan under Grant Nos. NSTC 113-2112-M-006-009-MY2 (CNK), 110-2124-M-006-006-MY3 (CSL), 112-2124-M-006-009 (CSL), 113-2112-M-007-033 (AF), 112-2112-M-213-029(AC) and 114-2112-M-213-021(AC). AF acknowledges support from the Yushan Fellow Program under the Ministry of Education of Taiwan and Grant No. JP22K03535 from Japan Society for the Promotion of Science(JSPS). ARS thanks the National Science and Technology Council(NSTC) of Taiwan for a post-doctoral fellowship under Grant No. NSTC 114-2811-M-213-006.

–

Publication: A. R. Shelke, C.-W. Chuang, S. Hamamoto, M. Oura, M. Yoshimura, N. Hiraoka, C.-N. Kuo, C.-S. Lue, A. Fujimori, and A. Chainani, The nexus between negative charge-transfer and reduced on-site Coulomb energy in correlated topological metals (submitted to Phys. Rev. Lett.).

Presenters

  • Abhijeet R Shelke

    • National Synchrotron Radiation Research Center, Hsinchu 300092

Authors

  • Abhijeet R Shelke

    • National Synchrotron Radiation Research Center, Hsinchu 300092

  • C.- W Chuang

    • Experimentelle Physik VII, Universit¨at W¨urzburg, Am Hubland, D-97074 W¨urzburg
    • Experimentelle Physik VII, Universitat Wurzburg, Am Hubland, D-97074 Wurzburg,

  • S. Hamamoto

    • RIKEN SPring-8 Center, Hyogo 679-5148

  • M. Oura

    • RIKEN SPring-8 Center, Hyogo 679-5148

  • M. Yoshimura

    • National Synchrotron Radiation Research Center, Hsinchu 300092

  • N. Hiraoka

    • National Synchrotron Radiation Research Center, Hsinchu 300092

  • C.- N Kuo

    • Department of Physics, National Cheng Kung University, Tainan 70101

  • C.- S Lue

    • Department of Physics, National Cheng Kung University, Tainan 70101

  • Atsushi Fujimori

    • Univ of Tokyo
    • Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033

  • A. A Chainani

    • National Synchrotron Radiation Research Center
    • National Synchrotron Radiation Research Center, Hsinchu 300092