Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 80: Low-Dimensional Systems - Poster Session

TT 80.18: Poster

Mittwoch, 2. April 2014, 15:00–19:00, P2

Vibrational infrared spectroscopy of a charge-ordered κ-phase under pressure — Sarika Singh¹, Rebecca Beyer¹, •Tomislav Ivek^1,2, Matija Čulo², Rimma N. Lyubovskaya³, and Martin Dressel¹ — ¹1. Physikalisches Institut, Universität Stuttgart, Germany — ²Institut za fiziku, Zagreb, Croatia — ³Institute of Problems of Chemical Physics, Chernogolovka, Russia

Dimerized organic conductors from the κ-(BEDT-TTF)₂X family are regarded as prime examples of Mott physics in two dimensions. Due to highly frustrated electron-electron interactions within the half-filled band, their ground states vary from superconducting X=Cu[N(CN)₂]Br, over spin liquid insulator of X=Cu₂(CN)₃, to canted antiferromagnetic insulator X=Cu[N(CN)₂]Cl. The related phase diagrams are generally well-described by the Hubbard model with only on-site repulsion U. On the other hand, the recent addition to the family, the X=Hg(SCN)₂Cl, undergoes a phase transition into a charge order at 30 K and ambient pressure. This particular ground state is completely unexpected within the Hubbard model.

In order to examine the exotic charge-ordered phase of κ-(BEDT-TTF)₂Hg(SCN)₂Cl, we performed vibrational reflectance infrared measurements under hydrostatic pressure up to 11 kbar and at temperatures from 300 down to 10 K. By tracking the charge-sensitive ν₂₇(B_1u) molecular vibration we are able to map the molecular charges present in the p–T phase diagram. We discuss the effects of pressure on the charge order by taking into account the nearest-neighbor electron repulsion within the paired-electron crystal model.