Charge-density wave and three-dimensional Fermi surface in1T−TaSe2studied by photoemission spectroscopy

Critical electronic structures controlling phase transitions induced by lithium ion intercalation in molybdenum disulphide

“…This is generally associated with two mechanisms: first, electrons are injected into previously unoccupied d-states, increasing the electron density on Mo and nesting the Fermi surface simultaneously, and second, the electron density is spatially modulated accompanied by a periodic lattice distortion (PLD) with complicated ionic patterns featured by reduced symmetry. Different from the electron self-modulation in such CDW materials as NbSe 2 , TiSe 2 and TaSe 2 [56][57][58], the modulation of electron density in Li-intercalated MoS 2 requires outer electron injection and depends on the symmetry of host matrix (1T or 2H). It is shown here that the Peierls instability exists also in the Li-intercalated 2H-MoS 2 , which results in the formation of a CDW weaker than that in the 1T counterpart.…”

Direct observation of an optically induced charge density wave transition in1T−TaSe2

“…In this paper, we will report on a study of the CDW phase transition in 1T-TaSe 2 between a commensurate phase (C-phase, q C = 0.225a* + 0.07b*) and an incommensurate phase (IC-phase, q IC = 0.278b*) induced by the fs-laser excitation. Theoretical analysis of the topology of the Fermi surface suggests that CDW in the IC-phase can be connected by the modulation wave vector as predicted by Peierls model [13][14], however, the nature of the C-phase and CDW transitions, is still under debate [15][16][17][18].…”

“…In previous literatures, it is demonstrated that the layered 1T-TaSe 2 crystals contain numerous of remarkable structural and physical phenomena in correlation with CDW and superconductivity [20][21][22]. 1T-TaSe 2 materials have a quasi-two-dimensional structure consisting of planes of hexagonally arranged Ta atoms, sandwiched by two Se layers coordinating the central Ta atom in an octahedral arrangement [15]. The structural modulations in association with CDW states occur dominantly in the a-b plane which depends evidently on the temperature and chemical compositions [21].…”

Te 5porbitals bring three-dimensional electronic structure to two-dimensional Ir0.95Pt0.05TeOotsuki1, Toriyama2, Pyon3 et al. 2014Phys. Rev. BSelf Cite15270View full textAdd to dashboardCite

“…The layered compounds tend to have flat cleavage surfaces which are suitable for angleresolved photoemission spectroscopy (ARPES) measurements, and the three-dimensional electronic structures can be observed by sweeping photon energy for ARPES. For example, the ARPES study on the classical 1T-TaSe 2 system has shown that the large Se-Se interaction between the layers and the strong covalency between the Ta 5d and Se 4p orbitals provide three-dimensional Fermi surfaces which play important roles in the charge density wave formation [1]. In the case of Fe-based superconductors, the origin of the spin and orbital order in the parent materials is still controversial and the three-dimensional multi-band Fermi surfaces observed by ARPES are key ingredients to understand the spin and orbital instabilities as well as the nodeless and nodal superconducting states [2].…”