Nonunitary multiorbital superconductivity from competing interactions in Dirac materials

Abstract

Unconventional superconductors represent one of the most intriguing quantum states of matter. In particular, multiorbital systems have the potential to host exotic nonunitary superconducting (NU SC) states. While the microscopic origin of nonunitarity is not yet fully solved, competing interactions are suspected to play a crucial role in stabilizing such states. The interplay between charge order and superconductivity has been a recurring theme in unconventionally superconducting systems, ranging from cuprate-based superconductors to dichalcogenide systems and even to twisted van der Waals materials. Here, we demonstrate that the existence of competing interactions gives rise to a nonunitary superconducting state. We show that the nonunitarity stems from a competing charge-ordered state whose interplay with superconductivity promotes multiorbital order. We establish this mechanism both from a Ginzburg-Landau perspective and from a fully microscopic self-consistent solution of a multiorbital Dirac material. Our results put forward competing interactions as a powerful mechanism for driving nonunitary multiorbital superconductivity.