  The development of van der Waals (vdW) crystals and their heterostructures
has created a fascinating platform for exploring optoelectronic properties in
the two-dimensional (2D) limit. With the recent discovery of 2D magnets, the
control of the spin degree of freedom can be integrated to realize 2D
spin-optoelectronics with spontaneous time-reversal symmetry breaking. Here, we
report spin photovoltaic effects in vdW heterostructures of atomically thin
magnet chromium triiodide (CrI3) sandwiched by graphene contacts. In the
absence of a magnetic field, the photocurrent displays a distinct dependence on
light helicity, which can be tuned by varying the magnetic states and photon
energy. Circular polarization-resolved absorption measurements reveal that
these observations originate from magnetic-order-coupled and thus
helicity-dependent charge-transfer exciton states. The photocurrent displays
multiple plateaus as the magnetic field is swept, which are associated with
different spin configurations enabled by the layered antiferromagnetism and
spin-flip transitions in CrI3. Remarkably, giant photo-magnetocurrent is
observed, which tends to infinity for a small applied bias. Our results pave
the way to explore emergent photo-spintronics by engineering magnetic vdW
heterostructures.
