Correlation Effects and Negative Charge Transfer in the Dirac Semi-metals CoTe2 and NiTe2
ABHIJEET RAVSAHEB SHELKE1*, C.-W. Chuang2, S. Hamamoto3, M. Oura3, M. Yoshimura1, N. Hiraoka1, C.-N. Kuo4,5, C.-S. Lue4,5, A. Fujimori1,6,7, A. Chainani1
1Condensed Matter Physics Group, National Synchrotron Radition Research Center, Hsinchu, Taiwan
2Experimentelle Physik, Universitat Wurzburg, Wurzburg, Germany
3RIKEN, SPring8, Hyogo, Japan
4Department of Physics, National Cheng Kung University, Tainan, Taiwan
5Taiwan Consortium of Emergent Crystalline Materials, National Science and Technology Council, Taipei, Taiwan
6Department of Physics, The University of Tokyo, Tokyo, Japan
7Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
* Presenter:ABHIJEET RAVSAHEB SHELKE, email:shelke.ab@nsrrc.org.tw
The layered 3d transition metal dichalcogenides (TMDs) CoTe2 and NiTe2 are topological Dirac Type-II metals. However, their d-bands do not show the expected correlation-induced band narrowing observed in CoO and NiO. In this study, we quantify the on-site Coulomb energy, Udd, using single-particle Co and Ni 3d partial density of states and the two-hole correlation satellite using valence band resonant photoemission spectroscopy (PES). The core-level PES and X-ray absorption spectra of CoTe2 and CoO validate their contrasting electronic parameters using cluster model simulations: Udd and charge transfer (CT) energy ∆ are (3.0 eV, -2.0 eV) for CoTe2, and (5.0 eV, 4.0 eV) for CoO, respectively. The d-p hybridization strength Teg for CoTe2 < CoO, and indicates that the reduced Udd in CoTe2 compared to CoO is not due to Teg but due to negative ∆. Yet, only because Udd > ∆, CoTe2 becomes a topological metal with p → p type lowest energy excitations. Using the same methodology, we also obtain a negative ∆ and reduced Udd for NiTe2 compared to NiO. The study reveals a connection between negative-∆ and a moderate Udd for achieving topological behavior in correlated metals.


Keywords: Correlated Topological Metals, on-site Coulomb Energy, Negative Charge Transfer, X-ray Photoemission Spectroscopy and X-ray Absorption Spectroscopy