Dresden 2017 – wissenschaftliches Programm
CPP 30.11: Vortrag
Mittwoch, 22. März 2017, 12:15–12:30, HSZ 201
Charge Carrier Dynamics at the Mott transition in κ-(BEDT-TTF)2Cu[N(CN)2]Br — •Tatjana Thomas1, Benedikt Hartmann1, Takahiko Sasaki2, and Jens Müller1 — 1Institute of Physics, Goethe University Frankfurt, Germany — 2Institute for Materials Research, Tohoku University, Sendai, Japan
The organic charge transfer salts κ-(ET)2X are considered as model systems for studying the Mott metal-insulator transition – a key phenomenon in the physics of strongly correlated electrons – in reduced dimensions. In particular, the influence of disorder on the criticality of the Mott transition recently has been a matter of debate. Partially deuterated κ-[(H8-ET)0.2(D8-ET)0.8]2Cu[N(CN)2]Br, which is located in the critical region of the phase diagram, can be fine-tuned through the Mott transition by utilizing a glass-like structural ordering transition of the ET molecules’ terminal ethylene groups. By applying different thermal relaxation protocols, both the ratio of W/U and a small degree of quenched disorder can be set at will, the former corresponding to changes in hydrostatic pressure of ∼200 bar. We employ fluctuation (noise) spectroscopy as a powerful tool to study the charge carrier dynamics at low frequencies. When crossing the S-shaped Mott transition line, surprisingly we observe a step-like increase of the resistance fluctuations in the metallic region. We discuss our results in terms of critical slowing down of the order parameter fluctuations  and electronic phase separation, and an extended region of the phase diagram where the fluctuations are non-Gaussian.
 B. Hartmann et al., Phys. Rev. Lett. 114, 216403 (2015).