Events

Abstract: Within ten years, flat band (FB) superconductivity has gained a huge interest for its remarkable features such as a direct connection to the concept of quantum geometry [1] and its possible realization in twisted bilayer graphene and other carbon based materials [2]. The main purpose of this talk is to give a small overview of the novel and unusual type of superconductivity associated with dispersionless bands. For this, we will first define the basic properties of FB states in the single electron picture by introducing the concept of quantum geometric tensor. Then, after showing the reliability of our mean field Bogoliubov-de-Gennes approach, we will discuss in detail the impact of quantum geometry on FB superconductivity in various (chains and ladders) low dimensional systems [3]. We will address as well a controversial topic that concerns the concept of coherence length in FB superconductors [4]. We will demonstrate hidden properties of the quasi-particle eigenstates leading to generalized sum-rules valid in disordered systems as well [5,6]. To describe more realistic materials, we will finish by a study of disordered/nanostructured two dimensional systems. We will in particular focus on the BKT temperature and reveal the resilience of FB superconductors to disorder [7]. Lastly, we will show how quantum geometry can provide an efficient strategy to reinforce the superconducting phase and hence the critical temperature in nanostructured lattices [8].

 

[1] S. Peotta and P. Törmä, Nature comunications, (2015)
[2] Y. Cao et al, Nature, (2018)
[3] M. Thumin and G. Bouzerar, Phys. Rev. B (2023)
[4] M. Thumin and G. Bouzerar, to appear in SciPost Physics (2025)
[5] M. Thumin and G. Bouzerar, EPL (2023)
[6] G. Bouzerar and M. Thumin, SciPost Physics (2024)
[7] G. Bouzerar and M. Thumin, to appear in Phys. Rev. B Letter (2025)
[8] M. Thumin and G. Bouzerar, Phys. Rev. B (2024)