Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 72: Low-Dimensional Systems: Poster Session
TT 72.12: Poster
Mittwoch, 18. März 2015, 15:00–18:00, Poster B
Mott metal-insulator transition induced by utilizing a glass-like structural ordering in low-dimensional molecular conductors — •Benedikt Hartmann1, Jens Müller1, and Takahiko Sasaki2 — 1Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany — 2Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
We utilize a glass-like structural transition in order to induce a Mott metal-insulator transition in the quasi-two-dimensional organic charge-transfer salt κ-(BEDT-TTF)2Cu[N(CN)2]Br. In this material, the terminal ethylene groups of the BEDT-TTF molecules can adopt two different structural orientations within the crystal structure, namely eclipsed (E) and staggered (S). When cooling through the glass transition at Tg≃ 75 K, a small fraction that depends on the cooling rate remains frozen in the S configuration. We demonstrate that, when thermally coupled to a low-temperature heat bath, a pulsed heating current through the sample causes a very fast relaxation with cooling rates at Tg of order several 1000 K/min. The freezing of the structural orientation causes a decrease of the electronic bandwidth W with increasing cooling rate, and hence a Mott metal-insulator transition as the system crosses the critical ratio (W/U)c of bandwidth W to on-site Coulomb repulsion U. Due to the glassy character of the transition, the effect is persistent below Tg and can be reversibly repeated by melting the frozen configuration upon warming above Tg. A simple model allows for an estimate of the energy difference between the E and S state as well as the cooling rate dependent difference in population.