2017/08/01 by Seho Yi, Zhenyu Zhang, Jun-Hyung Cho
Physics and Astronomy · #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevb.97.041413
published as Phys. Rev. B 97, 041413 (2018) · 8 pages, 10 figures
arxiv created 2017/08/01 · arxiv updated 2018/02/07
Two-dimensional layered transition metal dichalcogenide (TMDC) materials often exhibit exotic quantum matter phases due to the delicate coupling and competitions between the charge, lattice, orbital, and spin degrees of freedom. Surprisingly, we here present, based on first-principles density-functional theory calculations, the incorporation of all such degrees of freedom in a charge density wave (CDW) of monolayer (ML) TMDC 1T-TaS2. We reveal that the CDW formed via the electron-phonon coupling is significantly stabilized by the orbital hybridization. The resulting lattice distortion to the "David-star" superstructure constituted of one cental, six nearest-neighbor, and six next-nearest-neighbor Ta atoms is accompanied by the formation of quasimolecular orbitals due to a strong hybridization of the Ta t\rm 2g orbitals. Furthermore, the flat band of the quasimolecular orbital at the Fermi level has a spin splitting caused by an intramolecular exchange, yielding a full spin polarization with a band-gap opening. Our finding of the intricate charge-lattice-orbital-spin coupling in ML 1T-TaS2 provides a framework for the exploration of various CDW phases observed in few-layer or bulk 1T-TaS2.