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

Abstract

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 the strongly correlated electronic phase diagram with the first order Mott transition.