Ultracold Quantum Glassiness

Consider the ordinary rubber band. Though it might seem that a rubber band snaps back into shape after being stretched and released, this process actually requires several hours. During relaxation the length of the rubber band changes logarithmically, depending on how far the band was stretched. These two characteristics--aging, and slow and often logarithmic relaxation to equilibrium--capture the essential nature of glassiness, a phenomenon that surrounds and confounds us.

Currently our understanding of glassiness is incomplete. We are unsure if there are universal behaviors across different glassy systems, and we do not know how to predict how any particular glassy system will behave when perturbed. The challenge to understanding glassiness is that it involves drastically non-equilibrium states, and standard theoretical tools fail when applied to systems far from equilibrium.

Professor DeMarco’s research project aims to understand how disorder and inter-particle interactions combine to create quantum glassiness. The project involves creating an ultra-cold gas of atoms trapped in a disordered crystal of light, with an electron in each atom partially excited into a high-energy “Rydberg” state. The electron in these “Rydberg-dressed” atoms is tenuously bound more than 100billionths of a meter from the nucleus, 25,000 times farther away than usual. If the research group can achieve Rydberg dressing successfully, they will access a unique state of matter and be able to explore how the range of interactions affects and controls glassiness.

During his Center appointment Professor DeMarco will oversee the design and fabrication of two laser systems, carry out Autler-Townes spectroscopy to identify the wavelengths required to implement Rydberg dressing, integrate the laser systems into his lab’s existing optical-lattice apparatus, and measure the properties of interacting Rydberg-dressed atoms. This is a high-risk, high-payoff project with the potential to create a new tool for understanding quantum glassiness, contribute to fundamental physics, and have application to quantum materials such as superconductors and semiconductors.