Investigating quantum states and dynamics with X-ray spectroscopies @ CQP NYU



Our research involves the use of X-ray techniques for the discovery, characterization and manipulation of novel quantum states inside materials. When you bring many objects together, and allow them to change and interact according to a set of physical rules, surprising emergent phenomena can appear – like superconductuctivity in a metallic crystal, or like a snowflake built up from water molecules. Our group seeks to discover fundamentally new scenarios for emergence, built on new kinds of atomic scale "objects" and new sets of rules. The philosophies that drive this search include:

Topology + perturbations: New kinds of particle-like states can appear when nanoscale structure or many-body symmetry breaking is introduced to materials with topological electronic order. Topological quantum materials are known for a phenomenon called "bulk-boundary correspondence", which means that new quasiparticles appear at boundaries, or locations where the structure is highly disrupted.

Hundness: Hund’s rules can transform the atomic-scale quantum basis of a material. This sort of effect, recently termed "Hundness", can be significant for about 1/3rd of the elements on the periodic table, but is a point of failure for almost all modern simulation approaches.

Extreme valence states: Battery electrodes based on transition metals can be vastly modified by cycling in alkali atoms (particularly Li, Na). These electrodes have intrinsic value for society, and their chemical tunability can make them a primordial soup for the discovery of quantum materials. Battery-related materials that we are currently investigating (circa 2019) incorporate interesting topological and strongly correlated quantum states.

Here are a few references introducing techniques and physics we're interested in.

Our group also conducts projects related to numerically simulating the physical regimes revealed when X-rays interact with matter, and developing new technologies for X-ray science. Students and postdocs joining the group will be a part of the upcoming NYU Center for Quantum Phenomena, and will perform experiments at X-ray light sources such as the nearby Brookhaven National Lab and the Advanced Light source in Berkeley, California. Measurement techniques that we specialize in include angle resolved photoemission spectroscopy (ARPES) and resonant X-ray scattering (RXS/RIXS/REXS), both of which enable incisive in-situ investigation of the energy and momentum profiles of quantum states.

L. Andrew Wray Lab
Center for Quantum Phenomena
Department of Physics
New York University