Evolution of the 'High-(T sub c)' States at Ambient Pressure in beta-(BEDT-TTF)2I3

摘要

Annealing at about 110 K causes a change in the incommensurate superstructure inbeta-(BEDT-TTF)2I3. The effect of annealing on the ambient-pressure superconductivity in beta-(BEDT-TTF)2I3 was studied by magnetic susceptibility measurement. Both shielding and Meissner measurements revealed that two new superconducting states with T(c) at 7.5 K and 2 K appear as a result of annealing at ambient pressure. The authors assign the former corresponds to the 'high-T(c)' state. On the other hand, the latter superconducting state with T(c)=2 K should be regarded as a new superconducting state different from the original 'low-T(c)' state with T(c)=1.0-1.5 K. Thus beta-(BEDT-TTF)2I3 was found to exhibit three