Angle-resolved photoemission study of the evolution of band structure and charge density wave properties in RTe_ {3}(R= Y, La, Ce, Sm, Gd, Tb, and Dy)

Physical review. B, Condensed matter (Impact Factor: 3.77). 06/2008; 77(23). DOI: 10.1103/PhysRevB.77.235104
Source: arXiv

ABSTRACT We present a detailed angle-resolved photoemission spectroscopy (ARPES) investigation of the RTe3 family, which sets this system as an ideal “textbook” example for the formation of a nesting driven charge density wave (CDW). This family indeed exhibits the full range of phenomena that can be associated to CDW instabilities, from the opening of large gaps on the best nested parts of Fermi surface (up to 0.4 eV), to the existence of residual metallic pockets. ARPES is the best suited technique to characterize these features, thanks to its unique ability to resolve the electronic structure in k space. An additional advantage of RTe3 is that the band structure can be very accurately described by a simple two dimensional tight-binding (TB) model, which allows one to understand and easily reproduce many characteristics of the CDW. In this paper, we first establish the main features of the electronic structure by comparing our ARPES measurements with the linear muffin-tin orbital band calculations. We use this to define the validity and limits of the TB model. We then present a complete description of the CDW properties and of their strong evolution as a function of R. Using simple models, we are able to reproduce perfectly the evolution of gaps in k space, the evolution of the CDW wave vector with R, and the shape of the residual metallic pockets. Finally, we give an estimation of the CDW interaction parameters and find that the change in the electronic density of states n(EF), due to lattice expansion when different R ions are inserted, has the correct order of magnitude to explain the evolution of the CDW properties.

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    ABSTRACT: We use high-resolution synchrotron x-ray diffraction to uncover a second, low-temperature, charge density wave (CDW) in TbTe3. Its Tc2 = 41.0 ± 0.4 K is the lowest discovered so far in the rare earth telluride series. The CDWwave vectors of the high temperature and low temperature states differ significantly and evolve in opposite directions with temperature, indicating that the two nested Fermi surfaces are separated and the CDWs coexist independently. Both the in-plane and out-of-plane correlation lengths are robust, implying that the density waves on different Te layers are well coupled through the TbTe layers. Finally, we rule out any low-temperature CDW in GdTe3 for temperatures above 8 K, an energy scale sufficiently low to make pressure tuning of incipient CDW order a realistic possibility.
    Physical Review B 04/2013; 87:155131. · 3.66 Impact Factor
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    ABSTRACT: Rare-earth tri-tellurium RTe3 is a typical quasi-two-dimensional system which exhibits obvious charge-density-wave (CDW) orders. So far, RTe3 with heavier R ions (Dy, Ho, Er, and Tm) are believed to experience two CDW phase transitions, while the lighter ones only hold one. TbTe3 is claimed to belong to the latter. However, in this work we present evidences that TbTe3 also possesses more than one CDW order. Aside from the one at 336 K, which was extensively studied and reported to be driven by imperfect Fermi surface nesting with a wave vector q =(2/7c*), a new CDW energy gap (260 meV) develops at around 165 K, revealed by both infrared reflectivity spectroscopy and ultrafast pump-probe spectroscopy. More intriguingly, the origin of this energy gap is different from the second CDW order in the heavier R ions-based compounds RTe3 (R =Dy, Ho, Er, and Tm).
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    ABSTRACT: We employ an exact solution of the simplest model for pump-probe time-resolved photoemission spectroscopy in charge-density-wave systems to show how, in nonequilibrium the gap in the density of states disappears while the charge density remains modulated, and then the gap reforms after the pulse has passed. This nonequilibrium scenario qualitatively describes the common short-time experimental features in TaS2 and TbTe3 indicating a quasiuniversality for nonequilibrium "melting" with qualitative features that can be easily understood within a simple picture.

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