Bounds on the Superconducting Transition Temperature
Speaker: Mohit Randeria (The Ohio State University, USA, & Indian Institute of Science, Bengaluru, India)
Superconductivity is a striking phenomenon in which a system exhibits zero electrical resistance for temperatures below the transition temperature Tc. The question of understanding quantum mechanical limits on Tc is thus one of great fundamental and technological importance.
I will start with a detailed pedagogical introduction for non-specialists. I will describe recent progress on deriving exact upper bounds on the Tc of 2D superconductors applicable to a wide range of quantum materials and to ultracold atomic gases. I will illustrate the usefulness of these bounds by making contact with experiments on a variety of systems where standard BCS theory fails. Next, I will show how our bounds need to be generalized when the band structure exhibits non-trivial topology or lacks dispersion, i.e., flat band superconductivity. I will conclude by discussing why obtaining general upper bounds on Tc in 3D remains an open challenge.