Affiliation
IMDEA Madrid
Web
Talk Title
Evolution of Superconductivity in Twisted Graphene Multilayers
Abstract
Evolution of Superconductivity in Twisted Graphene Multilayers
Min Long,1, 2, Alejandro Jimeno-Pozo1, Héctor Sainz-Cruz1, Pierre A. Pantaleón1 †, and Francisco Guinea1, 3
1IMDEA Nanoscience, Faraday 9, 28049 Madrid, Spain
2Department of Physics and HKU-UCAS Joint Institute of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
3Donostia International Physics Center, Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
pierre.pantaleon@imdea.org
Abstract
Twisted double bilayer graphene is a superconductor. This recent, long-sought discovery can serve as a key in the maze of graphene superconductors. In this study, we adopt the Kohn-Luttinger-like, Random Phase Approximation (RPA) mechanism to investigate superconductivity along a transition from twisted double bilayer (TDBG) to twisted bilayer graphene (TBG) and from equal twist twisted trilayer graphene (eTTG) to TBG. We find critical temperatures of Tc~ 10 mK for TDBG, negligible for eTTG and 2 K for TBG. The higher critical temperature of TBG is mainly due to the extended nature of its wavefunctions in reciprocal space, which enhances Umklapp scatterings that are crucial propulsors of superconductivity. In contrast, states in the two outer layers of TDBG tend to localize in the first Brillouin zone, suppressing Umklapp scatterings and hindering superconductivity—a similar effect is found for eTTG. The order parameter of TDBG is like those of rhombohedral trilayer and Bernal bilayer graphene. Importantly, the Hartree potential, intricately linked to the charge distribution, plays a crucial role in influencing the superconducting properties of various graphene configurations. We observed that in narrow bands exhibiting a pronounced Hartree strength, there is a qualitative indication of significant critical temperatures. Our findings, along with previous research, put forward the Kohn-Luttinger-like, RPA mechanism as the leading candidate theory of superconductivity in graphene multilayers.