  We calculate the one-point function of certain chiral operators, known as
open Wilson lines, in the holographic Nambu-Jona-Lasinio (NJL) model at finite
temperature as well as finite chemical potential for quark (baryon) number
density. These operators are holographically dual to Euclidean string
worldsheets bounded by the flavor branes. Their one-point functions can serve
as order parameters for chiral symmetry breaking in these models. Analyzing the
behavior of the dual string worldsheets with respect to temperature and
chemical potential (or quark density) enables us to determine how the order
parameter depends on these parameters.
