PHASE TRANSITION ASSOCIATED WITH CHIRAL SYMMETRY BREAKING

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Phase transitions and critical phenomena have been a central subject of condensed matter physics for many years. We performed a variety of experimental studies to verify new types of phase transitions associated with chiral symmetry breaking.1.Chiral glass ordering in the YBCO ceramic superconductorsA new type of the ordered phase, a chiral glass(CG) phase, is predicted to appear in the high-T_c ceramic, which contains frustrated inter-grain Josephson junction networks. Aiming to detect the weak but finite internal fields produced by the freezed spontaneous chiral loop supercurrent in the CG phase, ZF-jμSR technique was applied. We succeeded in detecting an anomalous magnetic field in the superconducting state. At the present stage of analysis, however, the appearance of the weak field is not correlated with the occurrence of the predicted CG transition. The origin of this anomalous magnetic field is interesting but not clear at present.2.Chiral spin order in the frustrated magnetsWe synthesized a variety of frustrated magnetic systems such as 2D triangular lattice, 3D stacked triangular lattice, 1D chain with the competing interactions, and explored possible chiral spin order, in collaboration with many groups. We examined new technique to provide direct information on the chiral variable, including a possible application of the synchrotron X-ray diffraction to this problem.3.Quantum spin dynamics in nanoscale molecular magnetsIn nanoscale magnetic systems, quantum mechanical dynamics due to the discrete energy levels plays an important role. We studied molecular magnets, Fe12 and V15 with focusing on the determination of low-lying energy levels which have permanent importance in understanding their unique quantum magnetism.