High-pressure effects in fluorinated HgBa 2 Ca 2 Cu 3 O 8 + δ

We have measured the pressure sensitivity of T c in fluorinated HgBa 2 Ca 2 Cu 3 O 8 + δ (Hg-1223) ceramic samples with different F contents, applying pressures up to 30 GPa. We obtained that T c increases with increasing pressure, reaching different maximum values, depending on the F doping level, and decreases for a further increase of pressure. A new high T c record (166 K±1 K) was achieved by applying pressure (23 GPa) in a fluorinated Hg-1223 sample near the optimum doping level. Our results show that all our samples are at the optimal doping, and that fluorine incorporation decreases the crystallographic a -parameter concomitantly increasing the maximum attainable T c . This effect reveals that the compression of the a -axis is one of the keys that controls the T c of high-temperature superconductors.