Layer Sliding And Twisting Induced Electronic Transitions In Correlated Magnetic 1t‐Nbse₂ Bilayers

Abstract

Correlated 2D layers, like 1T‐phases of TaS2, TaSe2, and NbSe2, exhibit rich tunability through varying interlayer couplings, which promotes the understanding of electron correlation in the 2D limit. However, the coupling mechanism is, so far, poorly understood and is tentatively ascribed to interactions among the orbitals of Ta or Nb atoms. Here, it is theoretically shown that the interlayer hybridization and localization strength of interfacial Se pz orbitals, rather than Nb orbitals, govern the variation of electron‐correlated properties upon interlayer sliding or twisting in correlated magnetic 1T‐NbSe2 bilayers. Each of the layers is in a star‐of‐David (SOD) charge‐density‐wave phase. Geometric and electronic structures and magnetic properties of 28 different stacking configurations are examined and analyzed using density‐functional‐theory calculations. It is found that the SOD contains a localized region, in which interlayer Se pz hybridization plays a paramount role in varying the energy levels of the two Hubbard bands. These variations lead to three electronic transitions among four insulating states, which demonstrate the effectiveness of interlayer interactions to modulate correlated magnetic properties in a prototypical correlated magnetic insulator.

Prediction of intrinsic room-temperature ferromagnetism in two-dimensional CrInX2 (X = S, Se, Te) monolayers

“…Therefore, it is reasonable to consider CrInS 2 as a mixed Mott insulator and charge transfer (CT) insulator. 65,66 Through detailed investigation of the PDOS and band structures across the entire CrInX 2 system, it has been found that the bonding states progressively shift to higher energy levels due to the gradual decrease in Table 1 The lattice constant (a 0 ), Cr-X 1 bond length (l 1 ), Cr-X 2 bond length (l 2 ), Cr-X 1 -Cr bond angle (y 1 ), and Cr-X 2 -Cr bond angle (y 2 ) of the CrInX 2 monolayer at the GGA+U level. The band gaps (E g ) at the GGA+U and HSE06 levels electronegativity along the S -Se -Te series, while the antibonding states move to lower energy levels and cross the E F in the spin-down channels, consequently imparting metallic characteristics to CrInTe 2 .…”