[Zurück]

M. Dressel, A. Pustogow, R. Rösslhuber, Y. Saito, E. Uykur, Y. Tan, V. Dobrosavljevic:
"Dielectric Catastrophe at the Mott Transition";
Vortrag: SCES 2020, Brazil; 27.09.2021 - 01.10.2021.

A Mott insulator becomes metallic when the effect of correlations decreases. In the case of full frustration, a first-order phase transition is expected up to some critical endpoint. Above Tcrit there might be some crossover and quantum critical behavior [1]. But what happens below? We start with the quantum spin liquid k-(BEDT-TTF)2Cu2(CN)3 and tune the electronic bandwidth either by external pressure or by chemical substitution [2]. DC resistivity con-firms the insulator-metal transition (and even superconductivity in between). Optical spectroscopy reveals the development of the Drude-like contribution given evidence for coherent transport.
Most surprising, however, is the divergency of the dielectric permittivity e_1 at the Mott insulator-to-metal transition at temperatures T < Tcrit = 20 K with e_1 ~ 10^5 and more. We show that the dielectric catastrophe is a fingerprint of the first-order phase transition where metallic and insulating regions coexist spatially. The percolative nature of the Mott transition dominates the low-frequency behavior compared to the closing of the Mott-Hubbard gap seen in the infra-red range. All experimental trends are captured by dynamical mean-field theory of the single-band Hubbard model supplemented by percolation theory [3-5].
[1] A. Georges et al., Rev. Mod. Phys. 68, 13 (1996); M. Imada et al., Rev. Mod. Phys. 70, 1039 (2998).
[2] M. Dressel and S. Tomić, Adv. Phys. 69, 1 (2020); A. Pustogow et al., Nat. Mater. 17,773 (2018).
[3] A. Pustogow et al., npj Quantum Materials 6, 9 (2021)
[4] R. Rösslhuber et al., Phys. Rev. B 103, 125111 (2021)
[5] Y. Saito et al., J. Mat. Chem. C 9, doi 10.1039/d1tc00785h (2021)