Physics of Quantum Phase Transitions - Topological Quantum Criticality, Quantum Multi-Criticality and Novel Quantum Phases

阐明了新的量子临界性的本质，包括由拓扑变化表征的边缘量子临界性和量子多临界性，以及一阶跃迁的邻近效应。结果表明，在多临界点附近产生的零波数涨落的发散是几种前所未有的非费米液体性质的起源。零能隙半导体和拓扑绝缘体之间的量子相变具有自发对称性破缺和拓扑变化的双重特征，从而显示出新的临界性。阐明了边缘量子临界产生高温超导电性的机制。

Nature of novel quantum criticality including marginal quantum criticality and quantum multi-criticality characterized by topology changes as well as proximity effects of first-order transitions were clarified. It was revealed that the divergence of the fluctuations at zero wave number generated around the multi-critical points is the origin of several unprecedented non-Fermi liquid properties. Quantum phase transitions between zero-gap semiconductors and topological insulators are shown to have dual characters of spontaneous symmetry breaking and topology change and thus show novel criticality. We have elucidated the mechanism of high-temperature superconductivity generated by the marginal quantum criticality.