Record high (Tc) element superconductivity achieved in titanium

It is challenging to search for high T_c superconductivity (SC) in transition metal 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 T_c above 20 K in wide pressure range from 180 GPa to 240 GPa in titanium. The maximum T_c^{onset} above 26.2 K and zero resistance T_c^{zero} of 21 K are recorded, high values hitherto achieved among element superconductors. The H_{c2}(0) is estimated to be ~32 Tesla with coherence length 32 Å. The results show strong s-d transfer and band dominance, indicating electronic contributions to high T_c in SC. In contrast to the theoretical predictions based on pristine electron-phonon coupling scenario, the findings open a fresh promising avenue for rational design and discovery of high T_c superconductors among simple materials via pressure tuned unconventional mechanism.

Changling Zhang, Xin He, Chang Liu, Zhiwen Li, Ke Lu, Sijia Zhang, Shaomin Feng, Xiancheng Wang, Yi Peng, Youwen Long, Richeng Yu, Luhong Wang, Vitali Prakapenka, Stella Chariton, Quan Li, Haozhe Liu, Changfeng Chen, Changgan Jin