Dresden 2017 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 56: Poster Session: Low-Dimensional Systems
TT 56.18: Poster
Mittwoch, 22. März 2017, 15:00–19:00, P2-OG4
Pressure- and temperature-dependent optical investigations on α-(BEDT-TTF)2I3 — •Weiwu Li1, Ece Uykur2, Christine A. Kuntscher2, Dieter Schweitzer1, and Martin Dressel1 — 11.Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany — 2Experimentalphysik II, Universität Augsburg, 86135, Augsburg, Germany
The two-dimensional organic conductor α-(BEDT-TTF)2I3 exhibits a metal-insulator transition at Tco=135K with a charge-ordered ground state. This system is considered to host massless Dirac electrons under hydrostatic pressure as high as 1.5 GPa, which has been confirmed both theoretically and experimentally. For better understanding of the charge dynamics in the Dirac state, pressure-dependent infrared measurements have been performed previously. Unfortunately, limited by a maximum pressure of 1 GPa, no final evidence of the Dirac electrons could be found. As an extension to the previous measurements, we performed reflectivity measurements under pressure (up to 4GPa) between 100 and 8000 cm-1 down to 6 K by using diamond anvil cell. As a result, with increasing pressure we observed a Drude component developed below 600 cm-1 at the expense of the suppression of the mid-infrared band. The charge order still exists up to 1.6 GPa, where the conductivity already shows metallic behavior. At the highest pressure (4 GPa), the optical conductivity shows almost no temperature dependence below 90 K with a Drude term below 500 cm-1 and a constant conductivity extends up to 1500 cm-1, which point out the coexistence of the massive charge carriers and the massless Dirac electrons.