Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Poster Session: Correlated Electrons 1

TT 17.32: Poster

Monday, April 1, 2019, 15:00–18:30, Poster D

Charge Carrier Dynamics at the Metal-Insulator Transition in κ-(BEDT-TTF)₂Hg(SCN)₂Cl — •Tatjana Thomas, Harald Schubert, and Jens Müller — Institute of Physics, Goethe University Frankfurt, Germany

The organic charge-transfer salts κ-(ET)₂X are intensively studied due to their interesting electronic ground states, which are usually described within an effective-dimer model. In contrast, κ-(ET)₂Hg(SCN)₂Cl exhibits a metal-insulator transition at T_MI∼30 K due to charge ordering [1]. Dimerization of the ET molecules in combination with charge localization on one molecule within the dimer leads to a net dipole moment, so that the system exhibits ferroelectric order of electronic type [2]. Additional magnetic order would make the system even multiferroic, as it was recently discussed for κ-(ET)₂Cu[N(CN)₂]Cl [3]. Previous works on the latter salt showed that fluctuation (noise) spectroscopy provides new insights into the low-frequency charge carrier dynamics. Here, we present recent results on κ-(ET)₂Hg(SCN)₂Cl, where the normalized noise power spectral density shows an increase at the charge ordering transition. At low temperatures in the ferroelectric phase, we observe a strong electric field dependence of the fluctuation spectra. An observed spectral wandering is usually a hint for spatially correlated fluctuations. Measurements of the so-called second fluctuation spectrum indeed reveal a frequency dependence below the transition, indicating a switching between metastable states.
PRB 89, 075133
JPSJ 79, 011010
Nat. Mater. 11, 755