  We consider the fermionic (logarithmic) negativity between two fermionic
modes in the Schwinger model. Recent results pointed out that fermionic systems
can exhibit stronger entanglement than bosonic systems, exhibiting a negativity
that decays only algebraically. The Schwinger model is described by fermionic
excitations at short distances, while its asymptotic spectrum is the one of a
bosonic theory. We show that the two-mode negativity detects this confining,
fermion-to-boson transition, shifting from an algebraic decay to an exponential
decay at distances of the order of the de Broglie wavelength of the first
excited state. We derive analytical expressions in the massless Schwinger model
and confront them with tensor network simulations. We also perform tensor
network simulations in the massive model, which is not solvable analytically,
and close to the Ising quantum critical point of the Schwinger model, where we
show that the negativity behaves as its bosonic counterpart.
