NbSe2
Arxiv
Layer sliding and twisting induced electronic transitions in correlated magnetic 1T-NbSe2 bilayers
Mott and CT insulators are representative materials, like 1T-phases of TaS2, TaSe2 and NbSe2. In the strong-correlation limit of electron correlated systems, on-site Coulomb interactions split a half-filled band into two sub-bands, namely the lower (LHB) and upper Hubbard bands (UHB), forming a Mott or a CT insulator[13]. The governing coupling mechanism lies in the interlayer electronic hybridization of interfacial Se pz orbitals within a localized region of the David star, rather than previously supposed metal atoms dz2 orbitals. Subtle differences in interlayer hybridization vary the energy levels of the four Hubbard bands in the 1T-NbSe2 bilayer. Three electronic and two magnetic transitions among four insulating states were observed upon interlayer sliding or twisting, while three of the four insulating states are correlated ones. All these striking results highlight the importance of interlayer coupling in tunning correlated electronic states in NbSe2 bilayers.
Mirror twin boundaries (MTBs)[14,15] was demonstrate to be another strategy to introduce additional exotic electronic states in chalcogen-deficient 1H-MoS2[16], -MoSe2[14], and – MoTe2[17]monolayers. In some lattices with specific symmetries, such as kagome lattice, the intrinsic flat band leads to a high density of electron states. A TMD layer consisting of ordered and uniformly sized MTB triangles, namely an MTB-triangle lattice, could be a TMD phase exhibiting a well-defined lattice symmetry. Coloring-triangular (CT) lattice[18] in a MoTe2 (CT-MoTe2) monolayer comprise of uniform-sized and orderly arranged MTB triangles and normal MoTe2 domains embedded among MTBs. Dirac-like and flat electronic bands inherently existing in the CT lattice are identified by two broad and two prominent peaks. Further more, the CT-MoTe2 monolayer shows energy-dependent electronic Janus lattices, including the original atomic-lattice and an electronic Te pseudo-sublattice.
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