| Brief Bio of the Speaker |
Yu Li, graduated from the Donghua University in 2012, and got the PhD from the Institute of Physics, Chinese Academy of Sciences in 2018. From 2019 to now, he works as a postdoctoral in Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences (KITS, UCAS). His research interests mainly focused on the pairing mechanism on unconventional superconductivity (SC), such as: pairing symmetries in heavy-fermion SCs, Kerr effect in chiral SCs, and the exploration of the novel properties in the models of non-Fermi-liquid SC. |
Abstract | In many phase diagrams of unconventional superconductors (such as heavy fermions, cuprates, and iron-pnictides, etc.), superconductivity usually emerges out near the border of the magnetic ordering and involves a non-Fermi liquid normal state. My talk will show our studies from the spin-fluctuation approach and the non-Fermi liquid approach, separately. In the first part, based on the spin-fluctuation mechanism, I will introduce our phenomenological calculations to the typical heavy-fermion superconductors CeCu2Si2 [1], YbRh2Si2 [2], etc. [3]. In CeCu2Si2, our calculations first predict a (nodeless) s±-wave pairing, which providing a new angle to understand the debated pairing symmetry in superconducting CeCu2Si2 on experiments. And in YbRh2Si2, a nearly degenerate dx2-y2 and (px+ipy) wave pairing is predicted, which can provide a reference to understand the observed two-SC phases in YbRh2Si2 recently. In the second part, we start from the exactly-solvable Hatsugai-Kohmoto model [4], which shows an unconventional metallic state beyond the Landau’s paradigm and the Green’s function has the similar form as the Yang-Rice-Zhang’s ansatz for cuprates. With the on-site Hubbard interaction in momentum space, we introduce an emergent “two-band” description, and show how the Cooper instability on the “two-Fermi surfaces” occur simultaneously. Under the attractive pairing interaction, our calculation shows a novel ”two-stage” superconductivity, which may provide a new hint to approach the strongly-correlated superconductivity in theory. And if time permits, in the final part of the talk, I will briefly introduce our two proposals to understand the Kerr effect in chiral superconductivity [5,6]. [Reference]: [1] Y. Li, M. Liu, Z. Fu, X. Chen, F. Yang, Y.-F. Yang, Phys. Rev. Lett. 120, 217001 (2018). [2] Y. Li, Q. Wang, Y. Xu, W. Xie, Y.-F. Yang, Phys. Rev. B 100, 085132 (2019). [3] 李宇,盛玉韬,杨义峰, 物理学报 70, 017402 (2021). [4] Y. Li, V. Mishra, Y. Zhou, F.-C. Zhang, New J. Phys. 24, 103019 (2022). [5] Y. Li, Z. Wang, W. Huang, Phys. Rev. Research 2, 042027(R) (2020). [6] J.-L. Zhang, Y. Li, W. Huang, F.-C. Zhang, Phys. Rev. B 102, 180509(R) (2020). |
