【直播】复旦理论物理报告会 | 苏州大学康健、华中科技大学马怡秋

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本系列报告由复旦大学物理系主办，内含2场直播，分别于2021年4月23日9:30、10:30开始，授权蔻享学术进行网络直播。

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主   题：New perspective on the Bistritzer-MacDonald model and the return of itinerancy in twisted bilayer graphene

报告人：康健 （苏州大学）

时   间：2021年4月23日 9:30

个人简介

Jian Kang is currently a professor at Soochow university since 2019. He obtained his Ph.D. at Johns Hopkins University in 2013, under the advice of Prof. Tesanovic. In 2013 –2017, he was a postdoc in Prof. Fernandes's group at the University of Minnesota. In 2017-2019, he moved to the National high magnetic field laboratory in Florida, working with Prof. Vafek on the superconducting and correlated insulating phases discovered in twisted bilayer graphene. Until now, he has published more than 20 papers in APS journals. His main research field lies in theories of correlated electron systems and their collective behaviors.

报告摘要

The Bistritzer-MacDonald (BM) model predicted the existence of the narrow bands in the twisted bilayer graphene (TBG), and nowadays is a starting point for most theoretical works. In this talk, this model with Coulomb interactions will be reviewed from a rather different perspective. We treat this model as an effective field theory defined at atomic energy scale and find that the theory flows toward a fixed point in which the bands are exactly flat. Additionally, our theory explains the consistency of the magic angle between the theoretical value and the experimentally discovered one. With the Hamiltonian obtained, we further derived the exact excitation spectrum in the strong coupling limit at the even integer fillings. Combined with the variational method, we studied the Landau fan, the electron mass measured by quantum oscillations, and the recently discovered cascade transitions near the integer fillings. Our results not only qualitatively agree with the measurements, but also reveal the emergence of the Fermi liquid at the fractional fillings.

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主   题：Implementing of quantum amplifier in advanced gravitational wave detectors

报告人：马怡秋（华中科技大学）

时   间：2021年4月23日 10:30

个人简介

马怡秋，2008年华中科技大学学士学位，2016年澳大利亚西澳大学博士学位，研究领域：引力波探测器物理，2016-2019，加州理工学院博士后，研究领域：引力波探测器物理。2019-至今，华中科技大学物理学院任教。

报告摘要

The sensitivity of advanced ground-based gravitational wave detectors is limited by quantum noise. In this talk, we will first review the basic linear quantum measurement theory and its application on the detector analysis, then focus on how to use quantum amplifiers for boosting the sensitivity of gravitational wave detectors. Moreover, the implementation of a similar design concept in the axion detector (haloscope) will also be discussed.

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复旦大学物理系理论物理报告会

复旦理论物理报告会，每周五上午9:30举行，报告时间为一到两个小时。报告会旨在加强国内外理论物理前沿研究进展的互动，着重凝聚态物理、量子信息和原子分子光学等学科中重要的理论物理方面的最新进展和发展方向。通过加强交流，促进不同物理学科的交叉互通， 启发新的研究角度和新科学思想。提高研究生对前沿理论物理研究动向的敏感度和思考新物理问题尤其是交叉学科问题的积极性。

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