报告人：张超 中国科学技术大学访问学者

报告时间：12月4日（周一） 14:00
报告地点：唐敖庆楼C区532会议室

主办单位：原子与分子物理研究所

报告摘要:
It has been assumed for decades that high values of Tc from the electron-phonon coupling are impossible. At weak-to-intermediate coupling strength this result follows from the Migdal-Eliashberg theory, while at strong coupling, when bipolarons form, the transition temperatures are low because of the large effective mass enhancement. However, the latter conclusion was based on numerical solutions of the Holstein model. Here we present a different model with electron-coupling based on the displacement modulated hopping of electrons (bond Su-Schrieffer-Heeger model) and argue that much larger values of the bipolaron Tc can be achieved in this setup. We use an exact sign-problem-free quantum Monte Carlo approach to study the property of both Holstein and bond bipolarons with and without short- and long-range Coulomb interactions [1, 2]. The Tc in the bond bipolaron model generically and significantly exceeds typical upper bounds based on Migdal-Eliashberg theory or superfluidity of Holstein bipolarons. The key ingredient in this bipolaronic mechanism that gives rise to high Tc is the combination of light mass and small size of bipolarons. Our work establishes principles towards the design of high-Tc superconductors via functional material engineering.
Ref[1]: C. Zhang, J. Sous, D. R. Reichman, M. Berciu, A. J. Millis, N. V. Prokof’ev, and B. V. Svistunov, Physical Review X 13(1), 011010 (2023)
Ref[2]（accepted in Physical Review B Letter): J. Sous, C. Zhang, M. Berciu, D. R. Reichman, B. V. Svistunov, N. V. Prokof’ev, and A. J. Millis, arXiv:2210.14236

报告人简介：

张超，2018年12月获得美国俄克拉荷马大学物理学博士学位，后在德国萨尔大学，美国麻省大学阿默斯特分校从事博士后研究员工作。2021.06-2023.02为华东师范大学副研究员。现为中国科学技术大学访问学者。长期从事基于蒙特卡洛的方法对强相互作用的多粒子体的研究，具有扎实的研究基础和丰富的经验。截至目前已经取得了较为丰富的研究成果，在Physical Review X, Physical Review Letter, Physical Review B, Physical Review A, New Journal of Physics等国际知名期刊发表论文20篇，一作16篇。