Electronic materials driven far from equilibrium

That part of the electromagnetic spectrum that lies between microwaves and the mid-infrared is called the far infrared or terahertz (THz) band. Many materials have characteristic excitations and energy gaps at THz frequencies with the consequence that low power THz radiation has been widely used in the last two decades for applications in basic science, security, sensing and medicine [1]. However, only in the last few years have technologies been developed to allow the generation of ultrashort pulses of high power THz radiation in the laboratory so that the study of the dynamics of electrons, phonons and magnetisation in materials subjected to extremely intense THz fields, is relatively new [2]. With sub-picosecond MV/cm peak fields, it is possible to create atomic displacements equivalent to those obtained at GPa pressures and strongly drive electron spins with the associated magnetic field. The THz period is long compared with typical electronic motion so that free electrons see distorted potentials and accelerate to high energies before their motion is reversed.

In our laboratory we have recently built intense THz sources based on optical pumping of nonlinear crystals and photo-ionization of gases and now want to apply these to study materials driven far from equilibrium by intense, short THz pulses. The detailed material response can be studied using a variety of weak time resolved optical and THz probes. The PhD project will be concerned with using such pump-probe techniques to further our understanding of some of the properties of materials exhibiting strongly correlated electron behaviour, such as unconventional superconductors, Mott insulators and multiferroics.

You will have access to extensive laser spectroscopy facilities together with the opportunity to benefit from in-house expertise in the underlying theory and the wider interactions and training opportunities offered by the group’s affiliations with the Bath-Bristol Centre for Doctoral Training in Condensed Matter Physics.