The pressure-induced conducting behavior of the charge-transfer salts (BDA-TTP)2X [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene; X = ClO4·H2O, ClO4, BF4·H2O, BF4, and I3] has been investigated. With increasing pressure, the transition temperature to insulator observed in the ClO4·H2O, ClO4, BF4·H2O, and BF4 salts increases. On the other hand, the resistance of the I3 salt as a function of temperature at 10.0 kbar shows a drop attributable to a superconducting transition with an onset at 4.5 K. The superconducting transition temperature (Tc) can reach 8.2 K by applying a pressure of 10.3 kbar, but gradually decreases with further increases in the pressure.
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References
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Although we reported in ref. 6 that (BDA-TTP)2X (X = ClO4·H2O, ClO4, BF4·H2O, and BF4) are all 6-type salts, the reexamination of the crystal Structure of (BDA-TTP)2ClO4·H2O has revealed that the salt belongs to the α-type category. Structural details of the BDA-TTP salts described here will be reported separately.