Pressure-Induced Zero-Gap Semiconducting State in Organic Conductor α-(BEDT-TTF)_2I_3 Salt(Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties)

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We show a zero-gap semiconducting (ZGS) state in the quasi-two-dimensional organic conductor α-(BEDT-TTF)_2I_3 salt, which emerges under uniaxial pressure along the a-axis (the stacking axis of the BEDT-TTF molecule). The ZGS state is the state in which a Dirac cone with the band spectrum of a linear dispersion exists around the Fermi point connecting an unoccupied (electron) band with an occupied (hole) band. The spectrum exhibits a large anisotropy in velocity, which depends on the direction from the Fermi point. By varying the magnitude of several transfer energies of a tight-binding model with four sites per unit cell, it is shown that the ZGS state exists in a wide pressure range, and is attributable to the large anisotropy of the transfer energies along the stacking axis.
社団法人日本物理学会の論文
2006-05-15