Pressure Effect on BDA-TTP Conductors

The pressure-induced conducting behavior of the charge-transfer salts (BDA-TTP) 2 X [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene; X = ClO 4 ·H 2 O, ClO 4 , BF 4 ·H 2 O, BF 4 , and I 3 ] has been investigated. With increasing pressure, the transition temperature to insulator observed in the ClO 4 ·H 2 O, ClO 4 , BF 4 ·H 2 O, and BF 4 salts increases. On the other hand, the resistance of the I 3 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 (T c ) can reach 8.2 K by applying a pressure of 10.3 kbar, but gradually decreases with further increases in the pressure.