Venue: Small Lecture Theatre
Title: Feeling the strain: quadrupoles, octupoles and beyond
Abstract: Interactions can lead to a wide variety of ordered states in quantum materials, spanning from the obvious to incredibly subtle. For this talk, I will focus on the case of high rank multipole order of local atomic states, which are very much on the subtle end of the spectrum. I will particularly emphasize the importance of coupling to the associated order parameters as a means to measure the multipolar susceptibilities, and also, inside the ordered state, to induce quantum fluctuations via application of transverse effective fields. I will explain the very special roles that strain can play for each of the cases (quadrupolar, octupolar, hexadecapolar), and will outline several new experimental approaches in which the materials 'feel the strain' in very different ways. Along the way I will introduce a special case of an electro-nuclear quantum phase transition. The confluence of new measurement techniques and new materials also leads to possibilities for new applications; I will briefly outline one such application, based on a giant elastocaloric effect. Multipolar order, it would seem, is not only interesting from a fundamental perspective, but can also be useful.