Browsing by Author "Dobrosavljević, Vladimir"

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Open Access
Low-temperature dielectric anomaly arising from electronic phase separation at the Mott insulator-metal transition
(2021) Pustogow, Andrej; Rösslhuber, Roland; Tan, Yuting; Uykur, Ece; Böhme, Anette; Wenzel, Maxim; Saito, Yohei; Löhle, Anja; Hübner, Ralph; Kawamoto, Atsushi; Schlueter, John A.; Dobrosavljević, Vladimir; Dressel, Martin
Coulomb repulsion among conduction electrons in solids hinders their motion and leads to a rise in resistivity. A regime of electronic phase separation is expected at the first-order phase transition between a correlated metal and a paramagnetic Mott insulator, but remains unexplored experimentally as well as theoretically nearby T = 0. We approach this issue by assessing the complex permittivity via dielectric spectroscopy, which provides vivid mapping of the Mott transition and deep insight into its microscopic nature. Our experiments utilizing both physical pressure and chemical substitution consistently reveal a strong enhancement of the quasi-static dielectric constant ε1 when correlations are tuned through the critical value. All experimental trends are captured by dynamical mean-field theory of the single-band Hubbard model supplemented by percolation theory. Our findings suggest a similar ’dielectric catastrophe’ in many other correlated materials and explain previous observations that were assigned to multiferroicity or ferroelectricity.
Open Access
Rise and fall of Landau’s quasiparticles while approaching the Mott transition
(2021) Pustogow, Andrej; Saito, Yohei; Löhle, Anja; Sanz Alonso, Miriam; Kawamoto, Atsushi; Dobrosavljević, Vladimir; Dressel, Martin; Fratini, Simone
Landau suggested that the low-temperature properties of metals can be understood in terms of long-lived quasiparticles with all complex interactions included in Fermi-liquid parameters, such as the effective mass m⋆. Despite its wide applicability, electronic transport in bad or strange metals and unconventional superconductors is controversially discussed towards a possible collapse of the quasiparticle concept. Here we explore the electrodynamic response of correlated metals at half filling for varying correlation strength upon approaching a Mott insulator. We reveal persistent Fermi-liquid behavior with pronounced quadratic dependences of the optical scattering rate on temperature and frequency, along with a puzzling elastic contribution to relaxation. The strong increase of the resistivity beyond the Ioffe-Regel-Mott limit is accompanied by a ‘displaced Drude peak’ in the optical conductivity. Our results, supported by a theoretical model for the optical response, demonstrate the emergence of a bad metal from resilient quasiparticles that are subject to dynamical localization and dissolve near the Mott transition.