时间：12月12日（周五）15:00-17:00

　　地点：李薰楼468会议室

　　题目：Exotic quantum matters and their electronic structure characterization

　　报告人：朱燮刚　(中国工程物理研究院材料研究所)

　　摘要：Topological insulators, heavy fermion systems and iron-based superconductors can be catalogued into exotic quantum matters, which demonstrate novel and profound quantum phenomena in the sense of low dimensions, chemical doping, external pressure and magnetic filed. In this talk, I will briefly introduce the above exotic quantum matters and show our recent work on their electronic structure characterization by scanning tunneling spectroscopy and angle resolved photoemission spectroscopy. Our ongoing projects on those exotic quantum materials will also be reviewed.

　　个人简介：中国工程物理研究院材料研究所，副研究员。2006年获清华大学理学学士学位；2012年获清华大学理学博士学位；2012-2013年，丹麦奥胡斯大学物理系博士后；2014年3月，日本京都大学物理系访问学者；2012-2014年，中国工程物理研究院材料研究所，副研究员。研究工作主要集中在拓扑绝缘体、重费米子体系单晶薄膜制备及其电子结构表征，所利用的表征手段主要为低温扫描隧道显微术和实验室/同步辐射角分辨光电子能谱，研究成果已经发表在Nat. Phys., Adv. Mater., Phys. Rev. B, New J. Phys., Appl. Phys. Lett.等国际期刊上。

　　题目：Quantum Hall Liquids and Wigner Solids

　　报告人：张定　(清华大学物理系)

　　摘要：Ultra-clean 2-dimensional electron systems (2DES) under a strong magnetic field host a zoo of emergent states when sufficiently cooled: fractional quantum Hall liquids, stripe and bubble phases, Wigner crystalline states made of either electrons or holes. We report transport studies of these states in a semiconductor bilayer as well as in an oxide system. Firstly, a GaAs bilayer system will be discussed. Its additional layer degree of freedom engenders a novel quantum Hall state –theν=1/2+1/2 state [1, 2]. Also, the close spacing of the bilayer allows the realization of a sensitive technique to measure the chemical potential. Such a technique helps unveil the formation of Wigner crystalline states around integer quantum Hall states [3]. Finally, we report the observation of even denominator fractional quantum Hall states and reentrant phases in 2DES at the MgZnO/ZnO interface.

　　参考文献：

　　[1] Ding Zhang, Stefan Schmult, Vivek Venkatachalam, Werner Dietsche, Amir Yacoby, Klaus von Klitzing, and Jurgen Smet, Phys. Rev. B. 87, 205304 (2013).

　　[2] Ding Zhang, Xuting Huang, Werner Dietsche, Maik Hauser, and Klaus von Klitzing, Phys. Rev. B. 90, 085436 (2014).

　　[3] Ding Zhang, Xuting Huang, Werner Dietsche, Klaus von Klitzing, Jurgen Smet, Phys. Rev. Lett. 113, 076804 (2014).

　　个人简介：张定，2008年北京大学物理学院本科毕业，2014年德国马普固体所获得博士学位（导师为发现量子霍尔效应而获得诺贝尔物理学奖的Klaus von Klitzing教授），其专长为极低温强磁场下输运测量，主要研究了GaAs双量子阱中的量子霍尔态以及ZnO中二维电子系统的分数量子霍尔效应。目前在清华大学薛其坤院士团队工作。