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Charge-transfer properties and electron dynamics in ferromagnetic CoS2

Mahmoud Abdel-Hafiez1,2,3, Fredrik O. L. Johansson4,5,*, Anwesha Chakraborty6, Martin Pavelka7, Anirudha Ghosh8, D. A. Chareev9,10, A. N. Vasiliev11,12, Alexander Edström13,14,15, Anna Delin13,14,15 et al.

Olle Eriksson7,16, Debjani Karmakar6,7,17, and Dibya Phuyal15,†

  • *Present address: Department of Physics, Uppsala University, Box 516, SE-75121 Uppsala, Sweden.
  • †Contact author: dibya@kth.se
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Phys. Rev. B 112, 165115 – Published 14 October, 2025

DOI: https://doi.org/10.1103/vg4c-h785

Abstract

We investigated the element-specific electronic structure and charge-carrier dynamics of a single-crystal ferromagnet CoS2 with complementary x-ray spectroscopy techniques. Hard x-ray photoemission (HAXPES) is used to provide crucial information on the bulk electronic structure and chemical bonding in CoS2 that is compared against the isoelectronic paramagnet CoSe2. The Co 1s core-level line shows several satellite features for CoS2, showing explicit charge-transfer processes and local screening of the core hole by S ligands, whereas no such features are observed in CoSe2. The satellite structures indicate the electronic configuration of divalent Co2+ as a combination of d8Ḻ and d9Ḻ2 in addition to the nominal ionic d7 state, where Ḻ represents an S 3p hole. We employ resonant Auger spectroscopy across the S K-edge for CoS2 to obtain electron delocalization times to adjacent Co atomic sites. The fast carrier dynamics are attributed to strongly screened Coulomb interactions and hence a facile carrier delocalization. The strong hybridization formed between the Co 3d and S 3p states with pronounced charge-transfer character reflects a self-doped system with a finite density n of holes at the sulfur site (Ḻn), in line with recent models that indicate a negative charge-transfer energy for CoS2. In addition to HAXPES data, we also report on experimental and theoretical L-edge x-ray absorption and x-ray magnetic circular dichroism data for CoS2 that demonstrate multiconfiguration effects in the excitation process. To enable a direct comparison of the experimental spectra, we used density functional theory calculations to obtain the projected density of states to describe the ground-state electronic structure. The existence of fast carrier dynamics and strong charge-transfer properties, demonstrated in this study, highlights the unique nature of CoS2 with a wide potential in topological spintronics applications and integration in energy-related device platforms.

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Phys. Rev. B 112, 165115– Published 14 October, 2025
  • Received 24 February 2025
  • Revised 3 September 2025
  • Accepted 8 September 2025
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