  The quantum theory of antiferromagnetism in metals is necessary for our
understanding of numerous intermetallic compounds of widespread interest. In
these systems, a quantum critical point emerges as external parameters (such as
chemical doping) are varied. Because of the strong coupling nature of this
critical point, and the "sign problem" plaguing numerical quantum Monte Carlo
(QMC) methods, its theoretical understanding is still incomplete. Here, we show
that the universal low-energy theory for the onset of antiferromagnetism in a
metal can be realized in lattice models, which are free from the sign problem
and hence can be simulated efficiently with QMC. Our simulations show Fermi
surface reconstruction and unconventional spin-singlet superconductivity across
the critical point.
