Dresden 2017 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 47: Superconductivity: Properties and Electronic Structure 2
TT 47.1: Invited Talk
Wednesday, March 22, 2017, 15:00–15:30, HSZ 103
Interplay between CDW and Superconductivity: Effect of Pressure — •Matthieu Le Tacon — Karlsruher Institut für Technologie, Institut für Festkörperphysik, D-76021 Karlsruhe, Deutschland
I will focus on the interplay between superconductivity and charge density waves in superconducting cuprates and dichalcogenides. High resolution inelastic x-ray scattering was used to observe of a quasi-elastic *central peak* in underdoped YBa2Cu3O6.6, demonstrating the static nature of the CDW correlations, attributed to the pining of CDW nanodomains on defects. Low energy phonons also exhibit anomalously large superconductivity induced renormalizations close to the CDW ordering wave vector, providing new insights regarding the long-standing debate of the role of the electron-phonon interaction, a major factor influencing the competition between collective instabilities in correlated-electron materials. Relationship to the well-known anomalies in reported in the higher energy phonon branches will be discussed. Finally, the dependence of these effects with pressure will be reported.
Pressure has also been used to tune the ground state of a less correlated material, 2H-NbSe2. There a fast hardening of the soft phonon mode with pressure is observed, much faster than predicted by calculations carried out at the harmonic level. The inclusion of the full anharmonic potential in the calculation yields an excellent agreement with the experimental data and further allows demonstrating the major role of the electron-phonon interaction in the superconducting mechanism.