The conducting state of the quasi-two-dimensional organic conductor α-(BEDT-TTF)2I3 at ambient pressure is investigated with 13C NMR measurements, which separate the local electronic states at three nonequivalent molecular sites (A, B, and C). The spin susceptibility and electron correlation effect are revealed in a locally resolved manner. While there is no remarkable site dependence around room temperature, the local spin susceptibility gradually disproportionates among the nonequivalent sites with decreasing temperature. The disproportionation ratio yields 5:4:6 for A:B:C molecules at 140 K. Distinct site and temperature dependences are also observed in the Korringa ratio Ki(1/T1T)iKi-2 (i = A, B, and C), which is a measure of the strength and the type of electron correlations. The values of Ki point to sizable antiferromagnetic spin correlation. We argue the present results in terms of the theoretical prediction of the peculiar site-specific reciprocal-space (k-space) anisotropy on the tilted Dirac cone, and discuss the k-dependent profiles of the spin susceptibility and electron correlation on the cone.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2011 Sep 28|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics