Coupling of charge, lattice, orbital, and spin degrees of freedom in charge density waves in 1 T TaS_{2}
Abstract
Twodimensional layered transitionmetaldichalcogenide (TMDC) materials often exhibit exotic quantum phases due to the delicate coupling and competitions of charge, lattice, orbital, and spin degrees of freedom. Surprisingly, we here present, based on firstprinciples densityfunctional theory calculations, the incorporation of all such degrees of freedom in a charge density wave (CDW) of monolayer (ML) TMDC 1 T TaS_{2} . We reveal that this CDW accompanying the lattice distortion to the "Davidstar" (DS) superstructure constituted of one cental, six nearestneighbor, and six nextnearestneighbor Ta atoms is driven by the formation of quasimolecular orbitals due to a strong hybridization of Ta t_{2 g} orbitals. The resulting weakly overlapped nonbonding orbitals between the DS clusters form a narrow halffilled band at the middle of the CDW gap, leading to the Stonertype magnetic instability caused by an intramolecular exchange interaction. It is thus demonstrated that the Stoner parameter I corresponding to the effective onsite Coulomb interaction U opens a Mott gap. Our finding of the intricate chargelatticeorbitalspin coupling in ML 1 T TaS_{2} provides a framework for the exploration of various CDW phases observed in fewlayer or bulk 1 T TaS_{2} .
 Publication:

Physical Review B
 Pub Date:
 January 2018
 DOI:
 10.1103/PhysRevB.97.041413
 arXiv:
 arXiv:1708.00213
 Bibcode:
 2018PhRvB..97d1413Y
 Keywords:

 Condensed Matter  Mesoscale and Nanoscale Physics
 EPrint:
 8 pages, 10 figures