The interplay between superconductivity (SC) and charge or spin density wave (DW) appears in various strongly-correlated electron systems, including most high-Tc superconductors. Often these two phenomena coexist. The spatially uniform DW-SC coexistence may appear in the case of imperfect nesting of Fermi-surface (FS). Then the DW opens a gap in electron spectrum only on some FS parts. One could expect the exponential decrease of superconducting transition temperature Tc on DW background because of it exponential dependence on electron density of states (DoS) at the Fermi level according to BCS theory. However, usually, one observes a more complicated SC-DW interplay: the superconducting transition temperature Tc has a dome-like shape, being the highest at the quantum critical point (QCP) where the DW is suppressed by an external parameter. Tc of SC is often higher on the DW background than without DW. Why the enhancement of SC coupling by critical DW fluctuations overcomes the DoS reduction by DW? Surprisingly, the DoS at the Fermi level withstands the DW with imperfect nesting because the dispersion of remaining electrons on the Fermi surface is strongly renormalized. This explains the observed increase of SC transition temperature in DW state.

Biography
Prof. Pavel Grigoriev, obtained his Ph.D. (2001) and Doctor of Science (2015) degrees from the Landau Institute for Theoretical Physics. After the postdoctoral research under supervision of Lev Gor'kov at NHMFL (Tallahassee, USA) is a permanent researcher at Landau Institute. Since 2015 also a professor at National University of Science and Technology MISIS. His research interests include strongly correlated electron systems, magnetoresistance of layered conductors, neutron physics, liquid helium.

Uncovering the microscopic mechanisms of unconventional electronic orders and high-Tc superconductivity remains a central challenge in correlated-electron physics. In this talk, I will discuss two examples of how electronic structure and interactions can generate exotic quantum phases. First, I will present a theoretical scenario where a sublattice interference effect associated with van Hove singularities drive the long-sought loop-current order in kagome lattices, and discuss exotic pairing states in kagome metals. I will then introduce an itinerant framework in which scattering between states of opposite mirror parity unifies the understanding of magnetism and unconventional superconductivity in high-Tc multilayer nickelates.

Biography
Dr. Xianxin Wu received his Ph.D. from the Institute of Physics, Chinese Academy of Sciences, in 2016. From 2016 to 2022, he conducted postdoctoral research at the University of Würzburg and the Max Planck Institute for Solid State Research. In 2022, he joined the Institute of Theoretical Physics, Chinese Academy of Sciences. His research focuses on high-Tc superconductivity, topological superconductivity, strongly correlated electron systems, and topological phases of matter.