Role of intercalated cobalt in the electronic structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Co</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>/</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>NbS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Petar Popčević, Yuki Utsumi, I. Biało, Wojciech Tabiś, Mateusz A. Gala, Marcin Rosmus, J. Kołodziej, Natalia Tomaszewska, Mariusz Garb, H. Berger, I. Batistić, N. Barišić, L. Forró, Eduard Tutiš
Abstract
${\mathrm{Co}}_{1/3}{\mathrm{NbS}}_{2}$ is the magnetic intercalate of 2H-${\mathrm{NbS}}_{2}$ where electronic itinerant and magnetic properties strongly influence each other throughout the phase diagram. Here we report the angle-resolved photoelectron spectroscopy (ARPES) study in ${\mathrm{Co}}_{1/3}{\mathrm{NbS}}_{2}$. In agreement with previous reports, the observed electronic structure seemingly resembles the one of the parent material 2H-${\mathrm{NbS}}_{2}$, with the shift in Fermi energy of 0.5 eV accounting for the charge transfer of approximately two electrons from each Co ion into the ${\mathrm{NbS}}_{2}$ layers. However, in addition, and in contrast to previous reports, we observe significant departures that cannot be explained by the rigid band shift accompanied by minor deformation of bands: First, entirely unrelated to the 2H-${\mathrm{NbS}}_{2}$ electronic structure, a shallow electronic band is found crossing the Fermi level near the boundary of the first Brillouin zone of ${\mathrm{Co}}_{1/3}{\mathrm{NbS}}_{2}$. The evolution of the experimental spectra upon varying the incident photon energy suggests the Co origin of this band. Second, the Nb bonding band, found deeply submerged below the Fermi level at the $\mathrm{\ensuremath{\Gamma}}$ point, indicates that the interlayer hybridization is significantly amplified by intercalation, with Co magnetic ions probably acting as strong covalent bridges between ${\mathrm{NbS}}_{2}$ layers. The strong hybridization between orbitals that support the itinerant states and the orbitals hosting the local magnetic moments indicates the importance of strong electronic correlations, with the interlayer coupling playing an exquisite role.