  Mechanism of superconductivity (SC) in a purely interacting electron system
has been one of the most challenging issues in condensed matter physics. In the
BCS theory, the Landau's Fermi liquid is a normal state against which an SC
instability occurs once an \emph{additional} pairing force is added. We show
that in the doped Mott insulator an \emph{intrinsic} SC ground state
(specifically a Luther-Emery state in a finite-doping two-leg $t$-$J$ ladder)
can be directly turned into a Fermi-gas-like state by merely switching off the
hidden statistical sign structure via two schemes. It points to a new pairing
paradigm, %beyond the resonating-valence-bond scheme, which is an
"Amperean-like pairing" with a "stringlike" pairing force as shown by an
adiabatic continuity to a strong anisotropic limit of the model.
