Europhys. Lett.
Volume 73, Number 4, February 2006
Page(s) 594 - 600
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 13 January 2006
Europhys. Lett., 73 (4), pp. 594-600 (2006)
DOI: 10.1209/epl/i2005-10422-6

Coupling between quasiparticles and a bosonic mode in the normal state of $\chem{HgBa_2CuO_{4+\delta}}$

Y. Gallais1, M. Le Tacon2, 3, A. Sacuto2, 3 and D. Colson4

1  Department of Physics, Columbia University - New York, NY 10027, USA
2  Laboratoire Matériaux et Phénomènes Quantiques (UMR 7162 CNRS) Université Paris 7 - 2 place Jussieu, 75251 Paris, France
3  Laboratoire de Physique du Solide, ESPCI - 10 rue Vauquelin, 75231 Paris, France
4  Service de Physique de l'Etat Condensé, CEA-Saclay - 91191 Gif-sur-Yvette, France

received 14 October 2005; accepted in final form 13 December 2005
published online 13 January 2006

We report a doping-dependent study of the quasiparticles dynamics in $\chem{HgBa_2CuO_{4+\delta}}$ via Electronic Raman Scattering. A well-defined energy scale is found in the normal-state dynamics of the quasiparticles over a broad doping range. It is interpreted as evidence for coupling between the quasiparticles and a collective bosonic mode whose energy scale depends only weakly on doping. We contrast this behavior with that of the superconducting gap whose amplitude near the node continuously decreases towards the underdoped regime. We discuss the implications of our findings on the nature of the collective mode and argue that electron-phonon coupling is the most natural explanation.

74.72.-h - Cuprate superconductors (high-Tc and insulating parent compounds).
74.25.Gz - Optical properties.
74.72.Jt - Other cuprates, including Tl and Hg-based cuprates.

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