PHASE TRANSITION ASSOCIATED WITH CHIRAL SYMMETRY BREAKING

相变和临界现象多年来一直是凝聚态物理学的中心课题。我们进行了大量的实验研究来验证与手征对称性破缺相关的新型相变。1. YBCO陶瓷超导体中的手征玻璃有序化预测了一种新型的有序相--手征玻璃（CG）相，它存在于含有阻挫晶粒间约瑟夫森结网络的高温陶瓷中。为了探测CG相冻结自发手征环超电流产生的微弱但有限的内场，采用了ZF-j μSR技术。我们成功地探测到了超导状态下的异常磁场。然而，在目前的分析阶段，弱场的出现与预测的CG转变的发生无关。这种异常磁场的起源是有趣的，但目前还不清楚。2.阻挫磁体中的手征自旋序我们合成了各种阻挫磁性系统，如二维三角晶格，三维堆叠三角晶格，一维链与竞争相互作用，并探索可能的手征自旋序，与许多小组合作。我们研究了一种新的技术来提供手性变量的直接信息，包括同步辐射X射线衍射在这个问题上的可能应用。3.纳米分子磁体中的量子自旋动力学在纳米磁性系统中，由于离散能级引起的量子力学动力学起着重要的作用。我们研究了分子磁体Fe 12和V15，重点是确定低能级，这对理解它们独特的量子磁性具有永久的重要性。

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.