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Electron-Phonon Coupling in Charge Density Wave ZrTe 3

Electron-Phonon Coupling in Charge Density Wave ZrTe 3. Moritz Hoesch , Alexey Bosak, Alessandro Mirone, Michael Krisch European Synchrotron Radiation Facility ESRF Helmuth Berger École Polytechnique Fédérale de Lausanne, Suisse Dmitry Chernyshov Swiss-Norwegian Beamlines at ESRF.

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Electron-Phonon Coupling in Charge Density Wave ZrTe 3

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  1. Electron-Phonon Coupling in Charge Density Wave ZrTe3 Moritz Hoesch, Alexey Bosak, Alessandro Mirone, Michael Krisch European Synchrotron Radiation Facility ESRF Helmuth Berger École Polytechnique Fédérale de Lausanne, Suisse Dmitry Chernyshov Swiss-Norwegian Beamlines at ESRF ECRYS 2008 – Cargèse 25. 8. 2008

  2. 0 1 2 mm TCDW = 63 K ZrTe3 crystal structure and resistivity resistivity anomaly along a and c anisotropy ra / rb ~ 1 rc / ra ~10 prismatic (ZrTe3)∞ chains along b TCDW = 63 K, QCDW = (1/14 0 1/3 ) S. Takahashi et al. Journal de Physique 6 (1983) C3-1733 D.J. Eaglesham et al. J.Phys. C 17 (1984) L697 Te – Te chains along a ECRYS 2008 – Cargèse 25. 8. 2008

  3. c* a* (300) (400) (301) (401) qCDW = (0.07 0 0.3333) anomalous feature in the diffuse scattering diffuse scattering at SNBL BM01A reconstructed a*-c* plane MAR345 image plate detector T = 295 K (4.7 TCDW) T = 80 K (1.3 TCDW) (h0l)-plane (h0l)-plane ECRYS 2008 – Cargèse 25. 8. 2008

  4. qCDW to (4 0 1) dispersion across qCDW ECRYS 2008 – Cargèse 25. 8. 2008

  5. temperature evolution of the Kohn anomaly mean field theory observation close to giant Kohn anomaly leads to the lattice instability. ECRYS 2008 – Cargèse 25. 8. 2008

  6. origin of the diffuse scattering intensity IXS intensities from fit vs diffuse scattering intensity diffuse scattering is dominated by non-phonon scattering --> onset of order contributes strongly to diffuse scattering ECRYS 2008 – Cargèse 25. 8. 2008

  7. diffuse scattering around qCDW T > TCDW sharpening up of diffuse scattering T < TCDW growth of intensity of superstructure reflection ECRYS 2008 – Cargèse 25. 8. 2008

  8. power law exponents T < TCDW growth of intensity of superstructure reflection T > TCDW sharpening up of diffuse scattering intensity width inverse correlation length -> ν = 0.85 ± 0.2 order parameter -> β = 0.13 ± 0.03 TDS-regime ECRYS 2008 – Cargèse 25. 8. 2008

  9. conclusions • ZrTe3 shows a soft-mode driven Peierls transition. • Electron-phonon coupling leads to a Kohn Anomaly (KA) at high temperatures. • The coupling occurs in the mostly transverse acoustic phonon along qCDW. • The KA becomes giant and leads to the lattice instability as TCDW is approached. • Fluctuating CDW-order leads to enhanced diffuse scattering around qCDW. • The CDW order is three-dimensional with finite correlation along c* (out-of-plane). • The order parameter increases rapidly away from TCDW with a small power law:ωCDW withpower law 1/8 and intensity with β = 0.13 ± 0.03. • Transition is close to (blurred) first order transition, like (TaSe4)2I or blue bronze. ECRYS 2008 – Cargèse 25. 8. 2008

  10. b* a* c`* LDA calculation of the Fermi surface C. Felser et al. J. Mater Chem 8, 1787 the CDW superstructure colors: Fermi velocity convergent beam electron diffraction at 50 K D.J. Eaglesham et al. J.Phys. C 17 (1984) L697 chemical modulation “A” vanishes with time (no observed with x-rays) CDW-modulation “B”: qCDW ~ (1/14 0 1/3) CDW nesting vector ECRYS 2008 – Cargèse 25. 8. 2008

  11. LMTO theory K. Stöwe, F.R. Wagner, J. Solid St. Chem 138 (1998) 160 Fermi – surface map (ARPES) two hv = 45.2 eV lin. polarized T = 160 K Two quasi 1-dim. Fermi-surfaces: (a) hybridized Zr 4d along b* (b) Te 5px along a* M. Hoesch, X. Cui, K. Shimada (Hiroshima Univ.) unpublished data, see also T. Yokoya et al., PRB 71 (2005) 140504R. ECRYS 2008 – Cargèse 25. 8. 2008

  12. lattice dynamics at room temperature Inelastic x-ray scattering, resolution DE = 3.2 meV ZrTe3 phonon dispersions along a* and b* three kinds of modes are observed: - collective acoustic phonons - bending and torsion modes of the chains - optical modes of Te - atoms Raman data: A. Zwick, M.A. Renucci, A. Kjekhus, J. Phys. C: Solid State Phys. 13 (1980) 5603. ECRYS 2008 – Cargèse 25. 8. 2008

  13. comparison TDS vs IXS x 10-4 inelastic x-ray scattering (IXS) measures S(Q, w) and gives w thermal diffuse scattering (TDS) measures S(Q) ECRYS 2008 – Cargèse 25. 8. 2008

  14. reconstructed (hk0)-plane (0kl)-plane (h0l)-plane qCDW = (0.07 0 0.3333) survey of momentum space diffuse scattering at SNBL BM01A T = 295 K tomographic single crystal diffractometer MAR345 image plate detector where’s the soft mode? ECRYS 2008 – Cargèse 25. 8. 2008

  15. undulator source and Si(111) pre-monochromator lituned by thermal expansion sample detector E i Monochromator : Spot size: 250 x 60 mm2 (H x V) Si(n,n,n ), = 89.98 º E q B f n = 8 - 13 Analyser : Si(n,n,n ), = 89.98 º q B l constant n = 8 - 13 f IXS spectrometer schematic • reflection • DE (meV) • DQ (nm-1) • 5.5 • 0.05 • (8 8 8) • 3.0 • (9 9 9) • 1.7 • (11 11 11) • 0.9 • 0.15 • (13 13 13) ECRYS 2008 – Cargèse 25. 8. 2008

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