校庆60周年系列报告《威尔森比率与量子相变》 [2018-05-23]

报告题目：《威尔森比率与量子相变》

报 告 人：林海清教授（中国工程物理研究院北京计算科学研究中心）

报告时间：2018年5月25日（周五）下午4:00

报告地点：东区物理学院二楼学术报告厅

主办单位：物理学院

报告摘要：The Wilson ratio, defined as the ratio of magnetic susceptibility over heat capacity divided by temperature, could be used to characterize low temperature phases of a wide variety of materials. Using experimentally realized multi-species cold atomic gases as examples, we show that the Wilson ratios uniquely identify phases of quantum liquids, while providing universal scaling relations at the boundaries between phases. We also apply our analysis to the one-dimensional antiferromagnetic Heisenberg model and study its critical behavior as function of external magnetic field at finite temperatures. We found that the double-peak of the specific heat elegantly marks two crossover temperatures fanning out from the critical point, indicating three quantum phases: the Tomonaga-Luttinger liquid (TLL), quantum critical region and fully polarized ferromagnetic phases. Throughout the TLL phase the Wilson ratio RW = 4Ks (the Luttinger parameter) retains almost temperature-independent and thus captures the essence of the TLL. Our results fit well to the 1D spin-1/2 antiferromagnetic Cu(C₄H₄N₂)(NO₃)₂.
Acknowledgement: In collaborations with:
Yi-Cong Yu, Yang-Yang Chen, He Feng, Yu-Zhu Jiang,State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
Rudolf A. Römer,Department of Physics and Centre for Scientific Computing,University of Warwick, Coventry, CV4 7AL, UK
Xi-Wen Guan,Center for Cold Atom Physics, Chinese Academy of Sciences, Wuhan 430071, China
Department of Theoretical Physics, Research School of Physics and Engineering,
Australian National University, Canberra ACT 0200, Australia
Grants: NSAF U1530401

报告人简介：林海青教授现任中国工程物理研究院北京计算科学研究中心主任，从事计算方法、量子多体问题、量子纠缠和量子相变、磁性与超导物理的理论和计算研究工作。1981年中国科学技术大学学士。1983年美国Iowa州立大学理学硕士。1987年美国加州大学San Diego分校物理学博士。博士毕业后在美国Brookhaven 国家实验室 、Los Alamos国家实验室和University of Illinois at Urbana-Champaign物理系工作。1995年至2012年在香港中文大学物理系工作。2003年因在“发展和应用量子多体问题的计算方法”方面的贡献成为美国物理学会Fellow。