Superconductivity above 150 K in HgBa₂Ca₂Cu₃O_8+δ at high pressures

Abstract

RECENTLY, superconductivity at >130 K was reported^1,2 in multiphase samples of the compound system HgBa₂Ca_n−1Cu_nO_2n+2+δ (Hg-12(n−l)n) with n = 1, 2, 3,.... Single-phase Hg-1223 was subsequently synthesized and found to be superconducting at a record temperature of 135 K (ref. 3). It remains to be seen if a much higher transition temperature (T_c) than 135K can be achieved in this compound system. The application of pressure generally increases the T_c of underdoped layered cuprates, with a pressure derivative of T_c that decreases with increasing doping^4,5. Preliminary studies on Hg-1223⁶ showed a pressure-induced increase in T_c without any sign of saturation up to 17 kbar. Here we report the observation of superconductivity at up to 153 K in Hg-1223 at 150 kbar, with a main transition at 147 K. This observation provides an indication that superconductivity at >150 K may be possible in this system at ambient pressure, if suitable forms of chemical substitution can be found.