  Based on DFT+U and Berry curvature calculations, we study the electronic
structures and topological properties of 3d transition metal (TM) atom (from Ti
to Co) adsorbed germanene (TM-germanene). We find that valley-polarized
anomalous hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn,
or Co atom on its surface. A finite valley hall voltage can be easily detected
in its nanoribbon, which is important for valleytronics devices. Moreover,
different valley-polarized current and even reversible valley Hall voltage can
be archived by shifting the Fermi energy of the systems. Such versatile
features of the systems show potential in next generation electronics devices.
