Analyses of thermal diffusivity data on complex insulators and on strongly correlated electron systems hosted in similar complex crystal structures suggest that quantum chaos is a good description for thermalization processes in these systems, particularly in the high temperature regime where the many phonon bands and their interactions dominate the thermal transport. Here we observe that for these systems diffusive thermal transport is controlled by a universal Planckian time scale $τ\sim \hbar/k_BT$, and a unique velocity $v_E$. Specifically, $v_E \approx v_{ph} $ for complex insulators, and $v_{ph} \lesssim v_E \ll v_{F}$ in the presence of strongly correlated itinerant electrons ($v_{ph}$ and $v_F$ are the phonons and electrons velocities respectively). For the complex correlated electron systems we further show that charge diffusivity, while also reaching the Planckian relaxation bound, is largely dominated by the Fermi velocity of the electrons, hence suggesting that it is only the thermal (energy) diffusivity that describes chaos diffusivity.
Microcanonical Operator Spectrum, BPS Chaos and Free Probability Theory
Dipartimento di Fisica, Università di Milano - Bicocca（米兰比可卡大学物理系）；INFN, sezione di Milano-Bicocca（意大利国家核物理研究所米兰比可卡分部）；Department of Physics and Photon Science, Gwangju Institute of Science and Technology（光州科学技术院物理与光子科学系）；Center for High Energy Physics, Peking University（北京大学高能物理中心）
Thermalization in a Height-Conserving Quantum Dimer Model
School of Physics and Material Engineering, Hefei Normal University（合肥师范学院物理与材料工程学院）；School of Physics and Astronomy, University of Leeds（利兹大学物理与天文学院）；Department of Physics, School of Science and Research Center for Industries of the Future, Westlake University（西湖大学理学院物理学系及未来产业研究中心）；Institute of Natural Sciences, Westlake Institute for Advanced Study（西湖高等研究院自然科学研究院）
