  A chiral quark-model approach is adopted to study the $\eta$ photoproduction
off the quasi-free neutron and proton from a deuteron target. Good descriptions
of the differential cross sections, total cross sections and beam asymmetries
for these two processes are obtained in the low energy region. For $\gamma
p\rightarrow \eta p$, the dominant resonances are $S_{11}(1535)$,
$S_{11}(1650)$, $D_{13}(1520)$, $D_{13}(1700)$ and $P_{13}(1720)$. While for
the $\gamma n\rightarrow \eta n$ process, the dominant resonances are
$S_{11}(1535)$, $S_{11}(1650)$, $D_{13}(1520)$, $D_{15}(1675)$ and
$P_{13}(1720)$. Furthermore, the $u$ channel backgrounds have significant
contributions to the $\eta$ photoproduction processes. The configuration
mixings in the $S_{11}(1535,1650)$ and $D_{13}(1520,1700)$ can be extracted,
i.e. $\theta_S\simeq 26^\circ$ and $\theta_D\simeq 21^\circ$. It shows that the
narrow bump-like structure around $W= 1.68$ GeV observed in $\gamma
n\rightarrow \eta n$ can be naturally explained by the constructive
interferences between $S_{11}(1535)$ and $S_{11}(1650)$. In contrast, the
destructive interference between $S_{11}(1535)$ and $S_{11}(1650)$ produces the
shallow dip around $W= 1.67$ GeV in $\gamma p\rightarrow \eta p$. The $S$ wave
interfering behaviors in the proton and neutron reactions are correlated with
each other in the quark model framework, and no new exotic nucleon resonances
are needed in these two reactions.
