1:30 pm VIA ZOOM
High-temperature topological superconductivity in twisted double layer copper oxide, Marcel Franz, University of British Columbia
A great variety of novel phenomena occur when two-dimensional materials, such as graphene or transition metal dichalcogenides, are assembled into bilayers with a twist between individual layers. As a new application of this paradigm, we consider structures composed of two monolayer-thin d- wave superconductors with a twist angle θ that can be realized by mechanically exfoliating van der Waals-bonded high-Tc copper oxide materials, such as Bi2Sr2CaCu2O8+δ. On the basis of symmetry arguments and detailed microscopic modelling, we predict that for a range of twist angles in the vicinity of 45deg, such bilayers form a robust, fully gapped topological phase with spontaneously broken time-reversal symmetry and protected chiral Majorana edge modes. When θ ≈ 45deg, the topological phase sets in at temperatures close to the bulk Tc ≃ 90 K, thus furnishing a long sought realization of a true high-temperature topological superconductor.