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 ansätz for the quark-gluon vertex and gluon propagator. We obtain the value of the sigma term σπN = 62(1)(2) MeV, where the first represents the systematic error due to our different ansätz for the quark-gluon vertex and gluon propagator and the second represents a statistical error in our linear fitting procedure. Our result favors a relatively large value and is consistent very well with the recent data obtained by analyzing the pion-nucleon scattering and pionic atom experiments. *
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