  We calculate the variation of the chiral condensate in medium with respect to
the quark chemical potential and evaluate the pion-nucleon sigma term via the
Hellmann-Feynman theorem. The variation of chiral condensate in medium are
obtained by solving the truncated Dyson-Schwinger equation for quark propagator
at finite chemical potential, with different models for the quark-gluon vertex
and gluon propagator. We obtain the value of the sigma term $\sigma_{\pi N}$ =
62(1)(2) MeV, where the first represents the systematic error due to our
different model for the quark-gluon vertex and gluon propagator and the second
represents a statistical error in our linear fitting procedure.
