Topological superconductivity in twisted cuprates and device applications inspired by their Josephson physics
"In this thesis we explore the physics of Moire heterostructures of few-layer d-wave superconductor thin films. We show that such a twisted bilayer stack exhibits spontaneous time reversal symmetry breaking near θ = 45o twist, leading to a chiral superconductor state with topological edge modes. We then discuss the signatures of this prediction in polar Kerr effect experiments and find that expected Kerr rotation is three orders of magnitude larger compared to strontium ruthenate, one of the most studied chiral superconductor candidates. Another experimental signature of this novel phase we predict in twisted cuprates turns out to be the superconducting diode effect, which has recently been observed in transport experiments. Inspired by this experimental observation and the Josephson current-phase behaviour of this system, we introduce a novel superconducting circuit element made out of arrays of Josephson junctions which can be printed on a superconducting chip relying on available fabrication technology for practical applications. Finally, we propose a novel superconducting qubit design and provide a comparison with proposals that are in wide use today."