（Record High Tc Elemental Superconductivity Achieved In Titanium ）
C. L. Zhang, X. He, C. Liu, Z. W. Li, K. Lu, S. J. Zhang, S. M. Feng, X. C. Wang, Y. Peng, Y. W. Long, R. ChengYu, L. H. Wang, V. Prakapenka, S. Chariton, Q. Li, H. Z. Liu, C. F. Chen, C. Q. Jin
It is challenging to search for high Tc superconductivity (SC) in transitionmetal elements wherein d electrons are usually not favored by conventional BCS theory. Here we report experimental discovery of surprising SC up to 310 GPa with Tc above 20 K in wide pressure range from 108 GPa to 240 GPa in titanium. The maximum Tc(onset) above 26.2 K and zero resistance Tc(zero) of 21 K are record high values hitherto achieved among element superconductors. The Hc2(0) is estimated to be ～32 Tesla with coherence length 32 ?. The results show strong s-d transfer and d band dominance, indicating correlation driven contributions to high Tc SC in dense titanium. This finding is in sharp contrast to the theoretical predications based on pristine electron-phonon coupling scenario. The study opens a fresh promising avenue for rational design and discovery of high Tc superconductors among simple materials via pressure tuned unconventional mechanism.