Seminar

Speaker
Simon Wall, ICFO Barcelona

Title
Phase transitions in quantum materials

Abstract
Quantum materials exhibit some of the most fascinating properties found in solids, such as high temperature superconductivity, insulator-metal phase transitions and colossal magnetoresistance. Despite extensive research, the origins of these properties remain poorly understood. In this talk, I will examine the case of vanadium dioxide (VO2), one of the first, and most studied “quantum” materials, which shows an insulator-metal phase transition close to room temperature.

In this talk I will discuss the results of two new techniques we have developed which enable us to gain deeper insights into quantum materials, and specifically discuss their application to VO2. I will discuss how resonant soft X-ray holography can be used to measure nanoscale phase separation in inhomogeneous films, and enables the direct observation of domain growth. I will then go on to hard X-ray probes that enable the measurement of non-equilibrium phase transitions on the atomic scale. By using time-resolved diffuse X-ray scattering, we show that disorder is a key component in the structural transition, even though the structural transition occurs within a few hundred femtoseconds.