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TT: Fachverband Tiefe Temperaturen
TT 35: Correlated Electrons: Quantum-Critical Phenomena - Experiment I
TT 35.2: Vortrag
Dienstag, 1. April 2014, 09:45–10:00, HSZ 204
Exploring new LuT2In compounds: Evidence for a structural quantum critical point — •Thomas Gruner, Dongjin Jang, Raul Cardoso, Manuel Brando, Gerhard Fecher, and Christoph Geibel — MPI CPfS, 01187 Dresden, Germany
Finding novel compounds with unconventional properties is one of the most appealing tasks in modern solid state physics. We recently studied the compounds LuPt2In and LuPd2In and discover that they present an exceptional opportunity for studying a structural quantum critical point (QCP). Up to now QCPs have been intensively studied in magnetic systems, while structural QCPs are rather scarce.
We synthesized both compounds to study their structural and electronic properties. We found that at high temperatures both compounds crystalize in the simple cubic Heusler structure. While LuPd2In retains this structure down to lowest T, in LuPt2In susceptibility χ(T), resistivity ρ(T) and T-dependent powder XR diffraction evidence a charge density wave type transition at about 450 K to a yet undetermined low T structure. The T dependence of the anomalies in χ(T) and ρ(T) indicate a 2nd order type transition. Substituting Pd for Pt in Lu(Pt1−xPdx)2In results in a continuous decrease of Ttrans, indicating a structural QCP at xQCP ≈ 0.55. Most interestingly we observed bulk superconductivity in the whole alloy series, with a clear maximum in the SC transition temperature at xQCP. Furthermore we found that the phonon contribution to the specific heat at low T also presents a clear maximum at xQCP, suggesting critical phonon softening. These results provide new insight into structural QCPs.