1. Infrared and Raman study of the charge-density-wave state in the rare-earth polychalcogenides RTe n Leonardo Degiorgi Laboratorium für Festkörperphysik ETH Zürich, Switzerland

2. Motivation ➠ Charge ordering in low dimensions (CDW, stripes, checkerboard) ➠ Impact of charge ordering on the lattice dynamics ➠ Interplay between electronic and phononic degrees of freedom ➠ Role played by the electron-phonon coupling ➠ Fermi surface instabilities (nesting)

3. DiMasi et al., Phys. Rev. B52, 14516 (1995) RTe 2 R 2 Te 5 The Rare-Earth Tellurides RTe n (n=2, 2.5 and 3) RTe 3

4. Reflectivity and Optical Conductivity Photon Energy (eV)  1 (  ) (  cm) -1 Photon Energy (eV) http://www.solidphys.ethz.ch/spectro/

5. Sacchetti et al., Phys. Rev. B74, 125115 (2006) Optical Reflectivity of RTe 3

6. Sacchetti et al., Phys. Rev. B74, 125115 (2006) Plasma Frequency and Single Particle Peak in RTe 3

7. Pressure Dependence of R(  ) in CeTe 3

8. Sacchetti et al., Phys. Rev. Lett. 98, 026401 (2007) CDW Gap: Applied versus Chemical Pressure Dependence X-ray experiment at ESRF

9. Raman Scattering EkEk E2E2 E1E1 ħωħω ħω’ E1E1 E2E2 ħωħω StokesAnti-Stokes

10. Raman Scattering in RTe 3 : Chemical versus Applied Pressure

11. Petzelt and Dvorak, J. Phys. C9, 1571 (1976) Order Parameter versus Integrated Intensity of the Raman Modes in RTe 3

12. Conclusions and Future Outlook Fermi Surface Gapping Tomonaga-Luttinger Liquid Equivalence between Chemical and Applied Pressure Phonon Dispersion and Kohn Anomaly

13. Acknowledgements Lavagnini Sacchetti Theory T. Giamarchi (University of Geneva) R. Monnier (ETH Zurich) B. Delley (PSI) Pfuner Experiment A. Perucchi E. Arcangeletti L. Baldassarre M. Baldini D. Di Castro P. Postorino S. Lupi (University La Sapienza Rome and ELETTRA Trieste) Samples I.R. Fisher N. Ru Y.K. Shin J.-H. Chu (Stanford University)