  No definitive evidence of spacetime supersymmetry (SUSY) that transmutes
fermions into bosons and vice versa has been revealed in nature so far.
Moreover, whether spacetime SUSY in 2+1 and higher dimensions can occur or
emerge in generic microscopic models remains open. Here, we introduce a lattice
realization of a \textit{single} Dirac fermion with attractive Hubbard
interactions that preserves both time-reversal and chiral symmetries. By
performing numerically-exact sign-problem-free determinant quantum Monte Carlo
simulations, we show that the interacting single Dirac fermion in 2+1
dimensions features a superconducting quantum critical point (QCP). More
remarkably, we demonstrate that the ${\mathcal N}$=2 spacetime SUSY in 2+1D
emerges at the superconducting QCP by showing that the fermions and bosons have
\textit{identical} anomalous dimensions 1/3, a hallmark of the emergent SUSY.
To the best of our knowledge, this is the first observation of emergent 2+1D
spacetime SUSY in quantum microscopic models. We further show some experimental
signatures which can be measured to test such emergent SUSY in candidate
systems such as the surface of 3D topological insulators.
