# Dresden 2006 – wissenschaftliches Programm

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# TT: Tiefe Temperaturen

## TT 3: Correlated Electrons: Quantum-Critical Phenomena

### TT 3.3: Vortrag

### Montag, 27. März 2006, 10:00–10:15, HSZ 301

**Metamagnetic quantum criticality in Sr**_{3}**Ru**_{2}**O**_{7}** studied by thermal expansion** — •P. Gegenwart^{1}, F. Weickert^{1}, M. Garst^{2}, R.S. Perry^{3,4,5}, and Y. Maeno^{4,5} — ^{1}Max-Planck Institute for Chemical Physics of Solids, Dresden, Germany — ^{2}Theoretical Physics Institute, University of Minnesota, USA — ^{3}School of Physics and Astronomy, University of St. Andrews, Fife KY16 9SS, Scotland — ^{4}International Innovation Center, Kyoto University, Japan — ^{5}Department of Physics, Kyoto University, Japan

We report low-temperature thermal expansion measurements on the bilayer ruthenate Sr_{3}Ru_{2}O_{7} as a function of magnetic field applied perpendicular to the Ruthenium-oxide planes. The field-dependence of the *c*-axis expansion coefficient indicates the accumulation of entropy close to 8 Tesla, related to an underlying quantum critical point. The latter is
masked by two first-order metamagnetic transitions which bound a regime of enhanced entropy. Outside this region the singular thermal expansion behavior is compatible with the predictions for a two-dimensional metamagnetic quantum critical end point (work available at cond-mat/0507359).

Helpful discussions with S.A. Grigera, A.P. Mackenzie, A. Rosch and P. Wölfle are gratefully acknowledged. P.G. thanks the Deutsche Forschungsgemeinschaft (DFG grant GE 1640/1-1) and Royal Society (UK) for support of his stay at the St. Andrews University, M.G. is supported by DFG grant GA 1072/1-1.