Prineha Narang1
Harvard University1
In this talk, I will focus on our newly introduced approaches to describe excited-states in quantum matter and predicting emergent states introduced by strongly non-equilibrium external drives. Specifically, I will discuss a class of exotic collective excitations which are unique to time-reversal symmetry breaking (TRSB) superconductors and propose a number of means by which these excitations can be experimentally detected, essentially a <i>collective mode spectroscopy</i> of TRSB superconductors. Building on this notion, I will show our recent work on how to construct “designer” collective modes <i>via</i> a proximity effect in an unconventional superconductor heterostructure. Specifically, our work considers using a conventional “boring” s-wave superconducting substrate to proximitize a monolayer unconventional superconductor. Above the monolayer transition temperature, the residual pairing interaction binds the proximitized quasiparticles into a well-defined collective mode. This new collective mode is morally equivalent to the particle-particle excitonic mode of Bardasis and Schrieffer. Previously this mode has been shown to have signatures in, for example, the Raman spectrum, near-field optical spectrum, and in certain optical cavity geometries. Thus, we envision using this proximity effect to study the form of the monolayer pairing interaction directly <i>via</i> spectroscopic methods, and suggest it would be particularly useful when conventional transport and interference methods fail. Taking this further, I will present generalizable avenues in using electromagnetic cavities and resonators to probe and control quantum matter with methods to treat electrons, photons and phonons on the same quantized footing to access new observables in strong light-matter coupling. Understanding the role of such light-matter interactions in the regime of strongly-correlated electronic systems is of paramount importance to fields of study across condensed matter physics, quantum optics, and quantum chemistry. Our theoretical and computational framework opens new routes by which the important problem of strongly-correlated quantum dynamics may be studied in these fields. Finally, I will give an outlook on driving correlated quantum systems far out-of-equilibrium to control the coupled electronic and lattice degrees-of-freedom and connect these recent predictions with ultrafast THz experiments underway.