报告人：马天星 北京师范大学物理学系教授

报告时间：6月3日10:00-12：00

报告地点：物理学院A311

主办单位：物理与电子学院

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    报告摘要：Using exact quantum Monte Carlo method, we identify the phase diagram of the half filled, the lightly doped and heavily doped graphene, which shows a rather rich physical properties. At half filling, the system is driven to a Mott insulator with antiferromagnetic long range order by increasing interaction, and a transition from a d+id pairing to a p+ip pairing is revealed, depends on the next-nearest hoping and the electronic fillings. We also examine the recent novel electronic states seen in magic-angle graphene superlattices. From the Hubbard model on a double-layer honeycomb lattice with a rotation angle θ=1.08 , we reveal that an antiferromagnetically ordered Mott insulator emerges beyond a critical U c  at half filling, and with a small doping, the pairing with d+id  symmetry dominates over other pairings at low temperature. The effective d+id  pairing interaction strongly increase as the on-site Coulomb interaction increases, indicating that the superconductivity is driven by electron-electron correlation. Our non-biased numerical results demonstrate that the twisted bilayer graphene share the similar superconducting mechanism of high temperature superconductors, which is a new and idea platform for further investigating the strongly correlated phenomena.

   马天星，出生于河南开封，北京师范大学物理学系教授，博士研究生导师。分别于2000年7月和2005年7月在北京师范大学获得学士和博士学位。2005年8月至2010年6月先后在复旦大学、德国马普所、香港中文大学从事凝聚态物理理论方面的博士后研究，曾在美国Los Alamos国家实验室、美国加州大学圣地亚哥分校、美国加州大学Davis分校等访问研究。2010年7月至今在北京师范大学物理学系工作。主要从事电子关联体系磁性和超导电性的研究，包括石墨烯、铁基超导体、有阻挫系统等，已在Phys. Rev. Lett.、Phys. Rev. B，Appl. Phys. Lett.等上发表60余篇学术论文，主持或完成多项国家自然科学基金面上项目、北京市委优秀人才项目、北京市自然科学基金项目等。