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Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 40: Poster Session Correlated Electrons

TT 40.29: Poster

Wednesday, March 13, 2013, 15:00–19:00, Poster D

Vibrational IR-spectroscopy of charge-ordered α-ET2I3 under pressure — •Armin Dengl1, Rebecca Beyer1, Tomislav Ivek1,2, and Martin Dressel111. Physikalisches Institut, University of Stuttgart, Germany — 2Institut za fiziku, P.O. Box 304, HR-10001 Zagreb, Croatia

One of the most important charge-ordered compounds is the quasi-2D organic conductor α-ET2I3. Its structure consists of alternating conducting cation (ET-molecules) and insulating anion (I3) layers. The compound exhibits a first-order metal-insulator phase transition at TMI=135 K which is accompanied by a horizontal striped charge ordering within the ET layer. For ambient pressure the charge distribution has been well investigated, so we turned our attention to pressure-dependent IR-spectroscopy. The asymmetric charge-sensitive vibration ν27 (B1u) is the superior mode to determine the molecular charge due to its high sensitivity of resonance frequency on charge.
We performed vibrational reflectance IR measurements under hydrostatic pressure up to 11 kbar for a temperature range from 10 to 300 K. For the insulating charge-ordered phase we determined the molecular charge for the charge rich molecules. By applying pressure, the phase transition gets suppressed to lower temperatures by (9 ± 0.5) K/kbar towards the metallic phase. The charges of the charge rich molecules do not show any dependence on temperature, but by increasing pressure, a linear shift to lower values can be observed.

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