  We reveal by first-principles calculations that the interlayer binding in a
twisted MoS2/MoTe2 heterobilayer decreases with increasing twist angle, due to
the increase of the interlayer overlapping degree, a geometric quantity
describing well the interlayer steric effect. The binding energy is found to be
a Gaussian-like function of twist angle. The resistance to rotation, an
analogue to the interlayer sliding barrier, can also be defined accordingly. In
sharp contrast to the case of MoS2 homobilayer, here the energy band gap
reduces with increasing twist angle. We find a remarkable interlayer charge
transfer from MoTe2 to MoS2 which enlarges the band gap, but this charge
transfer weakens with greater twisting and interlayer overlapping degree. Our
discovery provides a solid basis in twistronics and practical instruction in
band structure engineering of van der Waals heterostructures.
