Engineering higher-temperature superconductivity

Andrey Grankin and all

This work reviews our recent theoretical ideas along with related experimental results related to engineering non-equilibrium protocols and electromagnetic environments to enhance superconductivity in solid-state materials. First, I'll discuss a generalization of the Kennes, Millis et al's protocol of using phonon squeezing to strongly enhance superconducting Tc, in particular close to the dynamical lattice instabilities caused by driving. Second, I will briefly review recent ideas of using cavity structures to engineer electromagnetic environments more favorable to superconductivity compared to materials in free space. Finally, I will zero in on hyperbolic metamaterial structures, which have been experimentally shown to strongly enhance superconducting Tc and the critical magnetic field in various compounds. These effects are usually attributed to hyperbolic plasmons, but I will argue that the conventional theory is probably unreliable. Based on our work in progress, I will speculate that it is likely boundary phonons that help bootstrap superconductivity in such systems. However, at the moment the nature of enhancement of superconductivity in hyperbolic metamaterials remains a bit of a mystery.