  We investigate theoretically the effects of modulated periodic perpendicular
magnetic fields on the electronic states and optical absorption spectrum in a
monolayer black phosphorus (phosphorene). We demonstrate that different
phosphorene magnetic superlattice (PMS) orientations can give rise to distinct
energy spectra, i.e., tuning the intrinsic electronic anisotropy. The Rashba
spin-orbit coupling (RSOC) will develop a spin-splitting energy dispersion in
this phosphorene magnetic supperlattice. Anisotropic momentum-dependent carrier
distributions along/perpendicular to the magnetic strips are demonstrated, and
the manipulations of these exotic properties by tuning superlattice geometry,
magnetic field and the RSOC term (via an external electric field) are addressed
systematically. Accordingly, we find bright-to-dark transitions in the ground
state electron-hole pairs transition rate spectrum and PMS orientation
dependent anisotropic optical absorption spectrum. This feature offers us a
practical way to modulate the electronic anisotropy in phosphorene by magnetic
superlattice configurations and detect these modulation capability by using the
optical technique.
