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.

In a 2009 paper "Turbulence in Integrable Systems", Zakharov discussed weakly integrable systems which have an infinite, but not sufficient for the full integrability, number of invariants. An example is KP1 for which Zakharov wrote a kinetic equation describing wave turbulence, and which has an infinite number of invariants and thermodynamic equilibria. In the present talk, I will report on numerical simulations of this kinetic equation, in particular, a kinetic instability of a wavepacket, and relaxation to equilibrium characterised by a condensation into low-frequency waves.

Nonlocal phase-coherent transport via Majorana bound states, so-called teleportation, requires Coulomb blockade to suppress local Andreev reflection. We show that dissipation can replace the need for Coulomb blockade. We study a Kitaev chain coupled to a Markovian bath and identify a regime where the magnitude of nonlocal conductance contribution reach the local one. In this regime, the lowest-energy subspace is maximally mixed, reminiscent of a directly grounded nontrivial topological superconductor. Phase coherence is confirmed by Aharonov-Bohm oscillations. Our results establish dissipation as a tool for controlling quantum teleportation in Majorana systems.

We establish a correspondence between the free-field construction and the minimal-model construction of the Calabi–Yau sector of the four-dimensional heterotic string compactified on Berglund–Hübsch type Calabi–Yau manifolds and their orbifolds. For Fermat-type polynomials the Calabi–Yau vertex operators expressed in terms of free fields are shown to correspond to products of primary fields of ????=2 minimal models. Using this correspondence we verify modular invariance of the free-field construction and extend it to Berglund–Hübsch Calabi–Yau orbifolds, deriving the conditions on complete vertex operators that parallel those of the minimal-model construction [1]. [1] A. Belavin, D. Gepner, G. Makarov, Free-Field Construction of Heterotic String Compactified on Calabi–Yau Orbifolds via Correspondence with N=2 SCFT Minimal Models, Nucl. Phys. B 117668 (2026).

The Berry curvature effect in anomalous transport driven by statistical forces such as the gradient of temperature or chemical potential has been developed by Di Xiao et al in Phys. Rev. Lett. 97, 026603 (2006). This theory operates with spinless fermions. So, the Berry curvature, corresponding magnetic moment of wave packets and the magnetic field dependent density of states originate from the electron orbital degrees of freedom. We present an alternative derivation of the Berry curvature effect on charge, heat and as well on thermalelectric currents in altermagnets and noncentrosymmertric metals where the electron band dispersion possesses spin dependent band splitting.

The band spin splitting in the hexagonal altermagnet CrSb is established using the magnetic group formalism that allows to find the additional spin splitting missed in the frame of the exchange approximation.

Phys.Rev.B 114, 065130 (2026).

Altermagnets are substances with a momentum-dependent spin splitting of electron bands due to a specific crystal structure that is invariant under time reversal only in combination with rotations and reflections. The developed phenomenological approach allows to obtain a spectrum of electron bands in altermagnets corresponding to antiferromagnets with the same symmetry. We consider antiferromagnetic, weak ferromagnetic, and ferrimagnetic structures. The calculated Berry curvature of electron bands in the alterrmarnet with zero spontaneous magnetisation occurs an odd function of momentum whereas it is even in a weak ferromagnetic state. The Berry curvature in ferrimagnetic state is equal to zero.

In this work, we propose an algorithm for constructing orbifolds of Calabi-Yau manifolds of Berglund-Hubsch type. This approach allows us to obtain all mirror pairs for Calabi-Yau manifolds of this type. As an example, we considered one of the Fermat-type models, for which all its orbifolds and their mirror pairs were found, and also for each orbifold the number of generations of quarks and leptons was found, as well as the number of types of particles participating only in gravitational interaction, i.e. dark matter particles.