Pressure-dependent optical investigations of α-(BEDT-TTF)2I3: Tuning charge order and narrow gap towards a Dirac semimetal

R. Beyer, A. Dengl, T. Peterseim, S. Wackerow, T. Ivek, A. V. Pronin, D. Schweitzer, M. Dressel

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

Infrared optical investigations of α-(BEDT-TTF)2I3 have been performed in the spectral range from 80 to 8000 cm-1 down to temperatures as low as 10 K by applying hydrostatic pressure. In the metallic state, T>135 K, we observe a 50% increase in the Drude contribution as well as the mid-infrared band due to the growing intermolecular orbital overlap with pressure up to 11 kbar. In the ordered state, T<TCO, we extract how the electronic charge per molecule varies with temperature and pressure: Transport and optical studies demonstrate that charge order and metal-insulator transition coincide and consistently yield a linear decrease of the transition temperature TCO by 8-9 K/kbar. The charge disproportionation Δρ diminishes by 0.017e/kbar and the optical gap Δ between the bands decreases with pressure by -47 cm-1/kbar. In our high-pressure and low-temperature experiments, we do observe contributions from the massive charge carriers as well as from massless electrons to the low-frequency optical conductivity, however, without being able to disentangle them unambiguously.

Original languageEnglish
Article number195116
Number of pages13
JournalPhysical Review B
Volume93
Issue number19
DOIs
Publication statusPublished - 9 May 2016

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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