
TRR 360 Seminar:
Energy relaxation and dynamics in strongly correlated materials
N. Peter Armitage
February 13 @ 14:00 – 15:00
Energy relaxation and dynamics in strongly correlated materials
Prof. Dr. N. Peter Armitage
Johns Hopkins University, Baltimore, USA
If a physical system is perturbed from equilibrium, the rate that it equilibrates is an important measure of its physics. In condensed matter systems, we are used to measuring such rates in the context of linear response to electromagnetic fields. For instance, the rate that current decays in a metal after an electric field impulse can be related to the width of its low-frequency “Drude” response in the optical conductivity. The rate that polarization decays after polling a liquid with an E field corresponds to the width of the broad peak in the Debye relaxational functional form. In contrast, the rate of energy relaxation is a fundamental rate that governs many processes in solids, but which is unfortunately not measured straightforwardly via conventional electrodynamic linear response. However quite generically, this rate can be measured in non-linear chi3 spectroscopies. I will discuss recent technical developments in the form of THz range 2D coherent spectroscopy (and its relatives) that allow us to get new information about energy relaxation in correlated and topological metals, as well as disordered electron glasses. I will discuss a number of systems and phenomena in which unconventional dynamics and energy relaxation govern their low energy behavior. I will give number of examples of the power of these new techniques to strongly interacting metals, Dirac semimetals, collective modes in superconductors, electron glasses, and 1D spin chains.
[1] Fahad Mahmood et al., “Observation of a marginal Fermi glass”, Nature Physics (2021).
[2] D. Barbalas et al., “Energy Relaxation and Dynamics in the Correlated Metal Sr2RuO4 via Terahertz Two-Dimensional Coherent Spectroscopy”, Phys. Rev. Lett. 134, 036501 (2025).
[3] K. Katsumi et al., “Revealing novel aspects of light-matter coupling in terahertz two-dimensional coherent spectroscopy: the case of the amplitude mode in superconductors”, Phys. Rev. Lett. 132, 256903 (2024).
[4] R. Bhandia et al., “”Anomalous electronic energy relaxation and soft phonons in the Dirac semimetal Cd3As2“, Phys. Rev. B 110, 075131 (2024).
[5] R. Bhandia et al. “Energy and momentum relaxation through the Curie temperature in an itinerant ferromagnet”, https://arxiv.org/abs/2412.08749.