Quantum Cafe: Ashvin Vishwanath

Title: Topological Criticality and Anyon Superconductivity: Routes to Beyond BCS Superconductors

Abstract: I will discuss two general ideas – quantum criticality between topological phases and anyon superconductivity – which provide novel routes to achieving electron pairing and superconductivity. Unlike the traditional BCS route, these new mechanisms offer pathways to electron pairing in seemingly inhospitable conditions, leading to superconductors that don’t play by the usual rules-ones that not only appear in, but require, strong magnetic fields or time reversal symmetry breaking, and which could potentially persist to elevated temperatures. We make these ideas concrete by discussing the phase diagram of a Hubbard model, which features electrons hopping on a triangular lattice with a magnetic flux, alongside strong electron repulsion, which counterintuitively is shown to exhibit superconductivity. This apparent paradox illuminates the power of these novel mechanisms. Finally, I’ll connect these theoretical insights to real-world possibilities in moiré materials-engineered structures which could serve as the perfect playground for realizing these unconventional superconducting states.