  We studied the Ag-intercalated 3D topological insulator Bi$_{2}$Se$_{3}$ by
scanning tunneling microscopy/spectroscopy and angle-resolved photoemission
spectroscopy, combined with a first principles calculations. We demonstrate
that silver atoms deposited on the surface of Bi$_{2}$Se$_{3}$ are intercalated
between the quintuple layer (QL) units of the crystal, causing a expansion of
the van der Waals gaps and the detachment of topmost QLs from the bulk crystal.
This leads to a relocation (in the real space) of the the topological state
beneath the detached quintuple layers, accompanied by the emergence of
parabolic and "M-shaped" trivial bands localized above the relocated
topological states. These novel findings open a pathway to the engineering of
Dirac fermions shielded from the ambient contamination and may facilitate the
realization of fault-tolerant quantum devices.
