Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Transport: Molecular Electronics and Photonics (jointly with CPP, HL, MA, O)

TT 40.11: 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 [1] and electronic phase separation, and an extended region of the phase diagram where the fluctuations are non-Gaussian.

[1] B. Hartmann et al., Phys. Rev. Lett. 114, 216403 (2015).