  Superconductivity in the family of spinel oxides is very rare owing to their
robust Mott-insulating nature. About half a century ago, LiTi$_2$O$_4$ became
the first reported spinel compound to show superconductivity with a 12K
transition temperature. Since then, several unsuccessful attempts were made to
enhance the T$_c$ of this family of materials. However, a very recent
experiment [arXiv:2209.02053] has reported superconductivity at a higher
temperature (below 16K), in the V-doped Mg$_{1-\delta}$Ti$_2$O$_4$ thin surface
layer while its bulk counterpart remains Mott insulating. The superconducting
T$_c$ of this material is significantly higher compared to other engineered
MgTi$_2$O$_4$ thin films grown on different substrates. From our
first-principles analysis, we have identified that Mg-depletion significantly
reduces Jahn-Teller (JT) activity and antiferromagnetic superexchange at the
surface layer of V-doped MgTi$_2$O$_4$ due to considerable charge transfer
between various ions. The combined effect of a degraded antiferromagnetic order
and reduced JT activity weakens the Mottness of the system, leading to the
emergence of superconductivity at higher temperatures.
