Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                

Charge- and spin-density waves observed through their spatial fluctuations by coherent and simultaneous x-ray diffraction

V. L. R. Jacques, E. Pinsolle, S. Ravy, G. Abramovici, and D. Le Bolloc'h
Phys. Rev. B 89, 245127 – Published 23 June 2014
PDFHTMLExport Citation
Abstract
Authors
Article Text
  • INTRODUCTION
  • EXPERIMENTAL SETUP AND RESULTS
  • DISCUSSION
  • CONCLUSION
    • References

    Abstract

    Spatial fluctuations of spin-density wave (SDW) and charge-density wave (CDW) in chromium have been compared by combining coherent and simultaneous x-ray diffraction experiments. Despite their close relationship, spatial fluctuations of the spin and of the charge-density waves display a very different behavior: the satellite reflection associated to the charge density displays speckles while the spin one displays an impressive long-range order. This observation is hardly compatible with the commonly accepted magneto-elastic origin of CDW in chromium and is more consistent with a purely electronic scenario where CDW is the second harmonic of SDW. A BCS model taking into account a second-order nesting predicts correctly the existence of a CDW and explains why the CDW is more sensitive to punctual defects.

    • Figure
    • Figure
    • Figure
    • Figure
    • Received 25 October 2013
    • Revised 28 May 2014

    DOI:https://doi.org/10.1103/PhysRevB.89.245127

    ©2014 American Physical Society

    Authors & Affiliations

    V. L. R. Jacques1, E. Pinsolle1, S. Ravy2, G. Abramovici1, and D. Le Bolloc'h1

    • 1Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay, France
    • 2Synchrotron SOLEIL - L'Orme des Merisiers Saint-Aubin - 91192 GIF-sur-YVETTE CEDEX, France

    Article Text (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 89, Iss. 24 — 15 June 2014

    Reuse & Permissions
    Access Options
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      (a) Schematic Fermi surface section in the (001) plane. The red region is the electron pocket centered at Γ and the two blue regions are the holes pockets at H. The partial dispersion curves are assumed to be linear, so we consider three prisms with four surfaces each. The second-order nesting phenomenon is described with colored planes connecting surfaces. (b) The (001) plane containing the satellite reflections associated to the SDW located at QS=(0,1±δ,0) and the satellites associated to the CDW at QC=(1,1±2δ,0).

      Reuse & Permissions
    • Figure 2
      Figure 2

      Schematic drawing of the simultaneous diffraction experiment. Given an incident wave vector ki, there exists a sample orientation for which the QS and QC satellite reflections are simultaneously located on the Ewald sphere. As a consequence, both reflections can be measured only moving the detector, and not the sample. This particular geometry ensures that the probed volume is the same when probing the two reflection satellites at Qc and Qs.

      Reuse & Permissions
    • Figure 3
      Figure 3

      Comparison of SDW and CDW in chromium by using coherent and simultaneous diffraction. Here are the diffraction patterns through the maximum intensity of the CDW [QC=(1,1−2δ,0)] and SDW satellites [QS=(0,1−δ,0)]. (a) Simultaneous diffraction (SD) of the SDW satellite [beamsize=100μm×300μm (H)]. (b) Simultaneous and coherent diffraction of the CDW satellite (beamsize=10μm×10μm) and (c) coherent diffraction (CD) of the QS satellite (beamsize=10μm×10μm). (d) Profiles corresponding to the three patterns along the direction represented by the white dashed lines. In all cases, the QC satellite displays speckles, while no speckle is observed at QS. The maximum intensity obtained on the two reflections is 150 counts/pixel for the SDW reflection and 100 counts/pixel for the CDW reflection.

      Reuse & Permissions
    • Figure 4
      Figure 4

      Authorized paths between the electron and hole pockets (Q2kF) and the two hole pockets (Q4kF). Red circles are in-volved in the inelastic process. Black squares do not fulfill the necessary conditions and are not involved in the nesting: (a) in the perfect case and (b) in the case with defects where states at the border of the Brillouin zone in two 2α width strips are removed from the process. (c) The number of authorized paths between the electron and hole pockets (open circles) and between the two hole pockets (full circles) vs α.

      Reuse & Permissions
    ×

    Sign up to receive regular email alerts from Physical Review B

    Log In

    Cancel
    ×

    Search

    Article Lookup

    Paste a citation or DOI
    Enter a citation
    ×