Electronic Structure Change of NiS${}_{2-x}$Se${}_x$ in the Metal-Insulator Transition Probed by X-ray Absorption Spectroscopy

Abstract

The electronic structure change of NiS${}_{2-x}$Se${}_x$ as a function of Se concentration $x$ has been studied by Ni $L$-edge X-ray absorption spectroscopy (XAS). The XAS spectra show distinct features in Ni $L_3$ edge, indicating whether the system is insulating or metallic. These features can be semi-quantitatively explained within the framework of the configurational interaction cluster model (CICM). In the S-rich region, relatively large charge-transfer energy ($\Delta \sim 5$ eV) from ligand $p$ to Ni 3$d$ states and a little small $p$-$d$ hybridization strength ($V_{pd\sigma }\sim 1.1$ eV) can reproduce the experimental spectra in the CICM calculation, and vice versa in the Se-rich region. Our analysis result is consistent with the Zaanen-Sawatzky-Allen scheme that the systems in S-rich side ($x\le$ 0.5) are a charge transfer insulator. However, it also requires that the $\Delta$ value must change abruptly in spite of the small change of $x$ near $x$=0.5. As a possible microscopic origin, we propose a percolation scenario where a long range connection of Ni[(S,Se)${}_2$]${}_6$ octahedra with Se-Se dimers plays a key role to gap closure.

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References in corpus (3)

• Simple cubic random-site percolation thresholds for complex neighbourhoods
• Direct observation of the bandwidth control Mott transition in the NiS${}_{2-x}$Se${}_x$ multiband system
• Estimate of the Phase Transition Line in the Infinite-dimensional Hubbard Model

Cited by in corpus (6)

• Percolation thresholds on triangular lattice for neighbourhoods containing sites up-to the fifth coordination zone
• Site percolation thresholds on triangular lattice with complex neighborhoods
• Controlling spin-orbit coupling to tailor type-II Dirac bands
• Structural investigation of the insulator-metal transition in NiS${}_{2-x}$Se${}_x$ compounds
• Universality of random-site percolation thresholds for two-dimensional complex non-compact neighborhoods
• Lower limit of percolation threshold on a square lattice with complex neighborhoods