High pressure investigation of an organic three-dimensional Dirac semimetal candidate having a diamond lattice

Diamond lattice in single-component molecular crystals comprising tetrabenzoporphyrin neutral radicals

“…3(d)). Consequently, under the application of 2.4 GPa, the electrical resistivity remains low down to 2 K; the electrical resistivity is 160 O cm, which is considerably smaller than the value of 10 5 O cm reported previously for (ET)Ag 4 (CN) 5 under 14 GPa at 4.5 K. 11 Contrary to the ET cation radical systems, which are multi-component systems with counter anions, Co(tbp)(CN) 2 is a single-component system without counter ions or solvents. Therefore, the application of pressure might effectively reduce the intermolecular distance, leading to high electrical conductivity even in the Mott insulating state.…”

“…This could be attributed to the electron–electron correlation, which is similar to that for the previously reported systems comprising ET cation radicals. 10,11 However, the electrical resistivity at 300 K ( ρ 300 ) and activation energy ( E a ) of Co(tbp)(CN) 2 are substantially smaller than those of the ET-systems (Table 1). Then, electrical resistance was measured as a function of temperature at varying pressures up to 2.4 GPa (Fig.…”

“…Therefore, experiments were performed under high-pressure conditions up to 14 and 1.8 GPa for (ET)Ag 4 (CN) 5 and (ET)Cu[N(CN) 2 ] 2 , respectively, but the Dirac semimetal state was not confirmed. 10,11 To date, there are limited reports on molecular crystals comprising radicals that form the diamond lattice, and the investigations on Dirac electron systems are still in their nascent stage. Constructing new molecular crystals comprising radicals forming the diamond lattice can lead to the generation of new threedimensional Dirac electron systems.…”