V. DOBROSAVLJEVIC – 31 MARS
Bad Metal Behavior and Mott Quantum Criticality
Par Vladimir Dobrosavljevic, Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, USA
Jeudi 31 Mars, 11h, Salle des séminaires, 3ème étage, Batiment A4
Figure 1 : DMFT theory quantitatively explains the high temperature “Bad Metal” behavior for doped Mott insulators, where linear T-dependence of the resistivity is observed around the Mott-Ioffe-Regel (MIR) limit . Here our theory (left two panels) is compared with experimental data for a doped cuprate material. The thick orange line indicates the MIR limit.
According to early ideas of Mott and Anderson, the interaction-driven metalinsulator transition – the Mott transition – remains a sharp T=0 phase transition even in absence of any spin or charge ordering. Should this phase transition be regarded as a quantum critical point? To address this question, here we examine the phase diagram and transport properties of the maximally frustrated half-filled Hubbard model, in the framework of dynamical mean-field theory (DMFT). We identify a “quantum Widom line” (QWL) which defines the center of the corresponding quantum critical region associated with Mott metal-insulator transition in this model. The evolution of resistivity with temperature is then evaluated along trajectories following (parallel to) the QWL, displaying remarkable scaling behavior characteristic of quantum criticality. Precisely this kind of behavior was found in very recent experiments on organic Mott systems [1,2]. In the case of the doping-driven Mott transition, we show that the mysterious “Bad Metal” behavior (T-linear resistivity around the Mott-Ioffe-Regel limit) coincides with the Quantum Critical region of the Mott transition.
 Quantum criticality of Mott transition in organic materials, Tetsuya Furukawa,
Kazuya Miyagawa, Hiromi Taniguchi, Reizo Kato & Kazushi Kanoda, Nature
Physics, 9 Feb. 2015; doi:10.1038/nphys3235.