Topological superconductivity, ferromagnetism, and valley-polarized phases in moiré systems: Renormalization group analysis for twisted double bilayer graphene
Yi‐Ting Hsu, Fengcheng Wu, S. Das Sarma
Abstract
Recent experiments on twisted double bilayer graphene report evidence of uniform spin and valley orders as well as spin-triplet superconductivity. Here, the authors perform perturbative renormalization group analyses for electrons near Van Hove singularities to investigate competition among all possible instabilities. Importantly, it is crucial to include not only the contribution that is second order in the logarithm, but also the logarithmically divergent contributions, in order to avoid bias towards density waves in weakly nested systems. The authors find rich phase diagrams exhibiting ferromagnetism, valley-polarized phase, and topological superconductivity, which are tunable by experimentally relevant parameters.