报告摘要：

　　Symmetry, dimensionality, and interaction are crucial ingredients for phase transitions and quantum states of matter. As a prominent example, the integer quantum Hall effect (QHE) represents a topological phase generally regarded as characteristic for two-dimensional (2D) electronic systems, and its many aspects can be understood without invoking electron-electron interaction. The intriguing possibility of generalizing QHE to three-dimensional (3D) systems was proposed decades ago, yet it remains elusive experimentally. Here, we report for the first time clear experimental evidence for the 3D QHE, observed in bulk ZrTe5 crystals. Owing to the extremely high sample quality, the extreme quantum limit with only the lowest Landau level occupied can be achieved by an applied magnetic field as low as 1.5 T. Remarkably, in this regime, we observe a dissipationless longitudinal resistivity      accompanied with a well-developed Hall resistivity plateau   , where       is the Fermi wavelength along the field direction (z axis). This striking result strongly suggests a Fermi surface instability driven by the enhanced interaction effects in the extreme quantum limit. In addition, with further increasing magnetic field, both       and        increase dramatically and display an interesting metal-insulator transition, representing another magnetic field driven quantum phase transition. Our findings not only unambiguously reveal a novel quantum state of matter resulting from an intricate interplay among dimensionality, interaction, and symmetry breaking, but also provide a promising platform for further exploration of more exotic quantum phases and transitions in the 3D electronic systems. 

报告人简介：

　　张立源，南方科技大学物理系副教授，深圳量子科学与工程研究院兼职研究员。2007年博士毕业于佐治亚理工学院物理系，2007-2011年先后在美国普渡大学、布鲁克海文国家实验室、纽约州立大学石溪分校作博士后。2011年底回国，被聘为中国人民大学副教授。2014年到南方科技大学工作。主要从事凝聚态物理量子输运的研究，近期关注层状量子拓扑材料的电输运实验研究及其纳米器件的制备，发表期刊论文20余篇。