  The predictive power of the deformed relativistic Hartree-Bogoliubov theory
in continuum (DRHBc) with density functional PC-PK1 is demonstrated for
superheavy region ($101 \leqslant Z \leqslant 120$) by comparing with available
experimental and evaluated data in the AME2020. The DRHBc theory predicts 93
bound nuclei beyond the drip line $N = 258$ in the region of $106 \leqslant Z
\leqslant 112$, which form a stability peninsula. The odd-even differences
between odd-$N$ and even-$N$ nuclei are remarkable in the stability peninsula;
the number of bound odd-$N$ nuclei is less than that of bound even-$N$ nuclei,
and the one-neutron separation energy of an odd-$N$ nucleus is smaller than
those of its neighboring even-$N$ nuclei due to the blocking effect. The
deformation effect is indispensable for the reentrant stability beyond the drip
line by significantly affecting the structure of single-particle levels around
the Fermi energy. The interplay between deformation and pairing effects affects
the position where the odd-$N$ nucleus becomes bound in the stability
peninsula. By examining the deformation effect at different orders, it is found
that quadrupole deformation makes leading contribution to the appearance of
stability peninsula and the effects of hexadecapole and hexacontatetrapole
deformations are nonnegligible.
