Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena

TT 6.28: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

Capacitive dilatometry under Helium-gas pressure — •Christian Balz, Andreas Brühl, Rudra Sekhar Manna, Bernd Wolf, and Michael Lang — Physikalisches Institut, Goethe-Universität, D-60438 Frankfurt(M), SFB/TR49, Germany

Important interaction parameters of organic conductors can be tuned by applying moderate external pressure. For the κ-(ET)₂X salts, for instance, many interesting regions of the phase diagram can be traversed by applying pressure of only a few hundred bars (e.g., paramagnetic Mott insulator, antiferromagnetic Mott insulator, superconductor or paramagnetic metal), see, e.g., [1]. Furthermore, thermal expansion measurements have been particularly suitable for exploring phase transitions such as the Mott metal-insulator transition [2], so it is highly desirable to combine the two techniques. In a pilot study, we have performed ultra-high resolution thermal expansion measurements at room temperature and under pressures up to 4 bar by combining capacitive dilatometry with the Helium-gas pressure technique. In a first step, we were able to accurately reproduce the expected pressure-induced changes in the dielectric constant of Helium. In addition, we are assembling a cryostat, where the same type of capacitive dilatometer cell that was used in our pilot experiment will be located inside a pressure cell. With this setup, we target at performing ultra-high resolution thermal expansion (Δ l/l ≥ 10⁻¹⁰) measurements over wide ranges of temperatures and hydrostatic Helium-gas pressures up to 2.5 kbar.

[1] S. Lefebvre et al., Phys. Rev. Lett. 85, 5420 (2000)

[2] M. de Souza et al., Phys. Rev. Lett. 99, 037003 (2007)