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ETUDE DE COMPOSES QUASI-UNIDIMENSIONNELS A ONDE DE DENSITE DE CHARGE PAR MICROSCOPIE A EFFET TUNNEL

Abstract : This work lies within the scope of the study of low dimensional systems. We present a study of the local electronic properties of two quasi-one-dimensional (Q1D) charge-density wave (CDW) compounds, the blue bronze Rb0.3MoO3 and NbSe3, using scanning tunneling microscopy (STM), under ultra-high vacuum (UHV) and at low temperature. These materials were cleaved in-situ along their natural plane, (-201) for Rb0.3MoO3 and (100) for NbSe3. Our study shows that the spatial distribution of the CDWs at the surface can be qualitatively different from that of the bulk, and that an in-situ preparation of the surfaces of these compounds is required to give access to their true electronic properties. At Rb0.3MoO3 surface, the CDW was visualized by STM. A new phenomenon was observed: the qb=2kf component of the CDW wave vector is inhomogeneous at the surface. We propose that this effect results from the inhomogeneousness of the surface Fermi vector, due to the inhomogenous distribution of the alkali atoms on the surface, after cleavage of the material. The consequences of these results are discussed. Our STM measurements on NbSe3 show a first coherent study of the CDW states q1 and q2, and of their spatial distribution on the various chains of the structure. At low temperature, the existence of an interaction between the q1 and q2 CDWs is revealed by the appearance of a new superstructure. Lastly, while at the surface, the q1 CDW has a transition temperature (Tc) comparable with that in the bulk, the q2 CDW has a Tc that is 10 to 15K higher at the surface than the bulk value. Various mechanisms relying on specific surface effects are discussed.
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https://tel.archives-ouvertes.fr/tel-00126135
Contributor : Christophe Brun <>
Submitted on : Tuesday, January 23, 2007 - 5:20:28 PM
Last modification on : Thursday, January 11, 2018 - 6:14:35 AM

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  • HAL Id : tel-00126135, version 1

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Christophe Brun. ETUDE DE COMPOSES QUASI-UNIDIMENSIONNELS A ONDE DE DENSITE DE CHARGE PAR MICROSCOPIE A EFFET TUNNEL. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 2006. Français. ⟨tel-00126135⟩

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