Van Hove Singularity and Spontaneous Fermi Surface Symmetry Breaking in Sr_3Ru_2O_7(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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The most salient features observed around a metamagnetic transition in Sr_3Ru_2O_7 are well captured in a simple model for spontaneous Fermi surface symmetry breaking under a magnetic field, without invoking a putative quantum critical point. The Fermi surface symmetry breaking happens in both a majority and a minority spin band but with a different magnitude of the order parameter, when either band is tuned close to van Hove filling by the magnetic field. The transition is of second order for high temperature T and changes to first order for low T. The first order transition is accompanied by a metamagnetic transition. The uniform magnetic susceptibility and the specific heat coefficient show strong T dependence, especially a log T divergence at van Hove filling. The Fermi surface instability then cuts off such non-Fermi liquid behavior and gives rise to a cusp in the susceptibility and a specific heat jump at the transition temperature.
社団法人日本物理学会の論文
2007-07-15