Real space imaging of the metal-insulator phase separation in the band width controlled organic Mott system κ-(BEDT-TTF)2Cu[N(CN)2]Br

Systematic investigation of the electronic phase separation on macroscopic scale is reported in the organic Mott system κ-(BEDT-TTF)2Cu[N(CN)2]Br. Real space imaging of the phase separation is obtained by means of scanning micro-region infrared spectroscopy using the synchrotron radiation. The phase separation appears near the Mott boundary and changes its metal-insulator fraction with the substitution ratio x in κ-[(h-BEDT-TTF)1-x(d-BEDT-TTF)x]2Cu[N(CN)2]Br, of which band width is controlled by the substitution ratio x between the hydrogenated BEDT-TTF molecule (h-BEDT-TTF) and the deuterated one (d-BEDT-TTF). The phase separation phenomenon observed in this class of organics is considered on the basis of he strongly correlated electronic phase diagram with the first order Mott transition. (author)