Kenichiro HASHIMOTO
Charge ordering (CO) is a phenomenon in which electrons in solids crystallize into a periodic pattern of charge-rich and charge-poor sites owing to strong electron correlations. In geometrically frustrated systems, however, a glassy electronic state without long-range CO (the so-called charge-glass state) has been realized. In this talk, I will show that structural defects introduced by x-ray irradiation in θ-(BEDT-TTF)2RbZn(SCN)4 also promote the charge-glass formation. In order to examine the randomness effect on the charge crystallization process, we constructed a time-temperature-transformation (TTT) diagram for the x-ray irradiated samples by using the differential scanning calorimetry (DSC) technique as well as the time evolution measurements of the resistivity. Through the construction of the TTT diagram, we found that with increasing x-ray irradiation time, the charge crystallization time becomes slower and the nose temperature becomes lower. The present findings demonstrate that the randomness effect in addition to the geometrical frustration effect plays an important role in the charge glass formation, which are similar to other glass formation systems such as spin glasses.