Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 22: Correlated Electrons: Quantum-Critical Phenomena 2
TT 22.3: Vortrag
Mittwoch, 25. März 2009, 10:15–10:30, HSZ 03
Probing the quantum critical behavior of CeCoIn5 via thermal expansion measurements — •Sebastian Zaum1,2, Kai Grube1, Roland Schäfer1, Eric D. Bauer3, Christoph Meingast1, and Hilbert v. Löhneysen1,2 — 1Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe, Germany — 2Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany — 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
The heavy-fermion compound CeCoIn5 is an unconventional superconductor. Its tetragonal crystal structure leads to anisotropic superconducting properties with an upper critical field of Bc2 = 5 T and 11.8 T along the a- and c-axes, respectively. At its upper critical field Bc2 ∥ c, CeCoIn5 reveals a quantum critical point with pronounced deviations from Fermi-liquid behavior. We have measured the thermal expansion αi (i = a, c) and magnetostriction λi longitudinal and transverse to the magnetic field. As expected, αi/T changes its sign at Bc2 and diverges with decreasing temperature. The effect of the quantum critical behavior on αa, however, is qualitatively different from that on αc. While αc shows at T=0.3 K a crossover to a weaker divergence, αa does not change its singular behavior down to the lowest measured temperature of 50 mK.