<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>T</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math> up to 23.6 K and robust superconductivity in the transition metal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>δ</mml:mi><mml:mtext>−</mml:mtext><mml:mi>Ti</mml:mi></mml:math> phase at megabar pressure
Xuqiang Liu, Peng Jiang, Yiming Wang, Mingtao Li, Nana Li, Qian Zhang, Yandong Wang, Yanling Li, Wenge Yang
Abstract
We report a high superconducting transition temperature ${T}_{c}$ up to 23.6 K, renewing the highest value in transition metals, under high pressure in the elemental metal Ti, one of the top ten most abundant elements in the earth's crust. The ${T}_{c}$ increases monotonically from 2.3 K at 40.3 GPa to 23.6 K at 144.9 GPa. With further compression, a robust ${T}_{c}$ of $\ensuremath{\sim}23$ K is observed between 144.9 and 183 GPa in the $\ensuremath{\delta}$-Ti phase. The pressure-dependent ${T}_{c}$ can be well described by the conventional electron-phonon coupling (EPC) mechanism. Density functional theory calculations show the Fermi nesting and the phonon softening of optical branches at the $\ensuremath{\gamma}$-Ti to $\ensuremath{\delta}$-Ti phase transition pressure-enhanced EPC, which results in the high ${T}_{c}$. We attribute the robust superconductivity in $\ensuremath{\delta}\text{\ensuremath{-}}\mathrm{Ti}$ to the apparent robustness of its strong EPC against lattice compression. These results provide insight into exploring high-${T}_{c}$ elemental metals and Ti-based superconducting alloys.