  We theoretically study the effect of atomic nonlinearity on the tunneling
time in the case of an atomic Bose-Einstein condensate (BEC) traversing the
laser-induced potential barrier. The atomic nonlinearity is controlled to
appear only in the region of the barrier by employing the Feshbach resonance
technique to tune interatomic interaction in the tunneling process. Numerical
simulation shows that the atomic nonlinear effect dramatically changes the
tunneling behavior of the BEC matter wave packet, and results in the violation
of Hartman effect and the occurrence of negative tunneling time.
