  Spinel compounds have demonstrated rich functionalities but rarely shown
superconductivity. Here, we report the emergence of superconductivity in the
spinel $\mathrm{MgTi}_2\mathrm{O}_4$, known to be an insulator with a
complicated order. The superconducting transition is achieved by engineering a
superlattice of $\mathrm{MgTi}_2\mathrm{O}_4$ and $\mathrm{SrTiO}_3$. The onset
transition temperature in the $\mathrm{MgTi}_2\mathrm{O}_4$ layer can be tuned
from 0 to 5 K in such geometry, concurrently with a stretched $c$-axis (from
8.51 to 8.53 \AA) compared to the bulk material. Such a positive correlation
without saturation suggests ample room for the further enhancement.
Intriguingly, the superlattice exhibits isotropic upper critical field
$H_{\mathrm{c}2}$ that breaks the Pauli limit, distinct from the highly
anisotropic feature of interface superconductivity. The origin of
superconductivity in the $\mathrm{MgTi}_2\mathrm{O}_4$ layer is understood in
combination with the electron energy loss spectra and the first-principles
electronic structure calculations, which point to the birth of
superconductivity in the $\mathrm{MgTi}_2\mathrm{O}_4$ layer by preventing the
Ti-Ti dimerization. Our discovery not only provides a platform to explore the
interplay between the superconductivity and other exotic states, but also opens
a new window to realize superconductivity in the spinel compounds as well as
other titanium oxides.
