Charge Ordering in alpha-(BEDT-TTF)2I3 by synchrotron x-ray diffraction

TL;DR

This study uses synchrotron X-ray diffraction to reveal the charge ordering and structural changes in alpha-(BEDT-TTF)2I3, confirming theoretical predictions and elucidating the insulating phase as a 2k_F charge density localization.

Contribution

It provides the first direct experimental evidence of the horizontal stripe charge order in alpha-(BEDT-TTF)2I3 using synchrotron radiation.

Findings

Horizontal stripe charge order confirmed

Charge disproportion observed above transition temperature

Significant change in transfer integrals at phase transition

Abstract

The spatial charge arrangement of a typical quasi-two-dimensional organic conductor alpha-(BEDT-TTF)2I3 is revealed by single crystal structure analysis using synchrotron radiation. The results show that the horizontal stripe type structure, which was suggested by mean field theory, is established. We also find the charge disproportion above the metal-insulator transition temperature and a significant change in transfer integrals caused by the phase transition. Our result elucidates the insulating phase of this material as a 2k_F charge density localization.