We report propagation of exciton polaritons (EPs) in photoexcited nanofibers of thiacyanine dye over a few hundred micrometers at room temperature. We determine the complex refractive index along the nanofibers by fluorescence microscopy measurements on single nanofibers and observe its anomalous behavior due to the EP effect. The longitudinal-transverse splitting energy (ΔE(L-T)) is evaluated to be ∼1  eV. The large ΔE(L-T) and waveguide function of the nanofibers allow a millimeter propagation of EPs at room temperature, which is hardly realized in other systems.

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To elucidate the underlying nature of the hidden order (HO) state in heavy-fermion compound URu(2)Si(2), we measure electrical transport properties of ultraclean crystals in a high field, low temperature regime. Unlike previous studies, the present system with much less impurity scattering resolves a distinct anomaly of the Hall resistivity at H;{*} = 22.5 T, well below the destruction field of the HO phase = or approximately 36 T. In addition, a novel quantum oscillation appears above a magnetic field slightly below H;{*}. These results indicate an abrupt reconstruction of the Fermi surface, which implies a possible phase transition well within the HO phase caused by a band-dependent destruction of the HO parameter.

KCuCl3 is a three-dimensional coupled spin-dimer system and has a singlet ground state with an excitation gap ∆/kB = 31 K. High-field magnetization measurements for KCuCl3 have been performed in static magnetic fields of up to 30 T and in pulsed magnetic fields of up to 60 T. The entire magnetization curve including the saturation region was obtained at T = 1.3 K. From the analysis of the magnetization curve, it was found that the exchange parameters determined from the dispersion relations of the magnetic excitations should be reduced, which suggests the importance of the renormalization effect in the magnetic excitations. The field-induced magnetic ordering accompanied by the cusplike minimum of the magnetization was observed as in the isomorphous compound TlCuCl3. The phase boundary was almost independent of the field direction, and is represented by the power law. These results are consistent with the magnon Bose-Einstein condensation picture for field-induced magnetic ordering.PACS number 75.10.Jm

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