Coulomb correlations and two-channel conduction in CuIr2S4 and CuIr2Se4 compounds

Abstract The resistivity ρ of CuIr 2 S 4 and CuIr 2 Se 4 have been measured at temperatures from 2 to 300 K under hydrostatic pressures up to 2 GPa. The conductivity σ at low temperature in the insulating phase of CuIr 2 S 4 is expressed as follows: σ =exp[−( T i * / T ) 0.5 ]. The pressure dependence of the activation energy and metal–insulator transition temperature give evidence that Coulomb correlations are important. Appearance of the insulating phase in CuIr 2 Se 4 is at a lower pressure than it had been assumed. The total resistivity under pressure can be represented as the resistivity in two parallel channels: the metallic resistivity which is exponentially dependent on temperature and the semiconducting one. The effective cross-section of the semiconducting channel rapidly increases with pressure above 1 GPa.