Article

Novel mechanism of a charge density wave in a transition metal dichalcogenide.

Department of Physics, Applied Surface Physics State Key Laboratory, Fudan University, Shanghai 200433, China.
Physical Review Letters (Impact Factor: 7.73). 12/2007; 99(21):216404. DOI: 10.1103/PhysRevLett.99.216404
Source: arXiv

ABSTRACT The charge density wave (CDW) is usually associated with Fermi surfaces nesting. We here report a new CDW mechanism discovered in a 2H-structured transition metal dichalcogenide, where the two essential ingredients of the CDW are realized in very anomalous ways due to the strong-coupling nature of the electronic structure. Namely, the CDW gap is only partially open, and charge density wave vector match is fulfilled through participation of states of the large Fermi patch, while the straight Fermi surface sections have secondary or negligible contributions.

0 Bookmarks
 · 
169 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this article, we report the first successful preparation of single- and few-layers of tantalum diselenide (2H-TaSe2) by mechanical exfoliation technique. Number of layers is confirmed by white light contrast spectroscopy and atomic force microscopy (AFM). Vibrational properties of the atomically thin layers of 2H-TaSe2 are characterized by micro-Raman spectroscopy. Room temperature Raman measurements demonstrate MoS2-like spectral features, which are reliable for thickness determination. E1g mode, usually forbidden in backscattering Raman configuration is observed in the supported TaSe2 layers while disappears in the suspended layers, suggesting that this mode may be enabled because of the symmetry breaking induced by the interaction with the substrate. A systematic in-situ low temperature Raman study, for the first time, reveals the existence of incommensurate charge density wave phase transition in single and double-layered 2H-TaSe2 as reflected by a sudden softening of the second-order broad Raman mode resulted from the strong electron-phonon coupling (Kohn anomaly).
    Scientific Reports 09/2013; 3:2593. · 5.08 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report an optical study of transition metal dichalcogenide 2H-TaS2 and the Na intercalated superconductor NaxTaS2 over a broad frequency range at various temperatures. A clear gap feature was observed for 2H-TaS2 when it undergoes the charge-density wave (CDW) transition. The existence of a Drude component in sigma1(omega) below TCDW indicates that the Fermi surface of 2H-TaS2 is only partially gapped in the CDW state. The spectral evolution of two different NaxTaS2 crystals further confirms that the partial gap structure observed in 2H-TaS2 has a CDW origin. The CDW mechanism for 2H-TaS2 and the competition between CDW and superconductivity in the NaxTaS2 system are discussed.
    Physical review. B, Condensed matter 01/2007; 76(4). · 3.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on first-principles studies of lithium-intercalation-induced structural phase transitions in molybdenum disulphide (MoS2), a promising material for energy storage in lithium ion batteries. It is demonstrated that the inversion-symmetry-related Mo-S p-d covalence interaction and the anisotropy of d-band hybridization are the critical factors influencing the structural phase transitions upon Li ion intercalation. Li ion intercalation in 2H-MoS2 leads to two competing effects, i.e. the 2H-to-1T transition due to the weakening of Mo-S p-d interaction and the D 6h crystal field, and the charge-density-wave transition due to the Peierls instability in Li-intercalated 2H phase. The stabilization of charge density wave in Li-intercalated MoS2 originates from the enhanced electron correlation due to nearest-neighbor Mo-Mo d-d covalence interaction, conforming to the extended Hubbard model. The magnitude of charge density wave is affected by Mo-S p-d covalence interaction and the anisotropy of d-band hybridization. In 1T phase of Li-intercalated MoS2, the strong anisotropy of d-band hybridization contributes to the strong Fermi surface nesting while the d-band nonbonding with S-p facilities effective electron injection.
    Chinese Science Bulletin 58(14). · 1.37 Impact Factor

Full-text

Download
7 Downloads
Available from