Condensed Matter Seminar
I discuss the interplay between non-Fermi liquid behaviour and superconductivity near a quantum-critical point (QCP) in a metal. It is widely thought that the tendency towards superconductivity and towards non-Fermi liquid behaviour compete with each other, and if the pairing interaction is reduced below a certain threshold, the system displays a naked non-Fermi liquid QC behaviour. I show that the situation is more complex as there are multiple solutions for Tc at a QCP. For all solutions, except one, Tc vanishes when the pairing interaction drops below the threshold.
In the last six years the power conversion efficiency of solar cells made with metal halide perovskite semiconductors has soared from less than 7% to over 23%. Only four other families of semiconductors have ever reached this efficiency. Perovskites are very attractive compared to those families because they can be deposited from solution at low cost, function well even when they contain a high density of defects, and have the right bandgaps to be used in tandem solar cells.