  We consider nonreciprocal supercurrent effects in Josephson junctions based
on multiband superconductors with a pairing structure that can break
time-reversal symmetry. We demonstrate that a nonreciprocal supercurrent can be
generally achieved by the cooperation of interband superconducting phase
mismatch and interband scattering as well as by multiband phase frustration.
The effect of interband impurity scattering indicates that the amplitude and
sign of the nonreciprocal supercurrent are sensitive to the interband phase
relation. For the case of a three-band superconductor, due to phase
frustration, we show that the profile of the supercurrent rectification is
marked by a hexagonal pattern of nodal lines with vanishing amplitude.
Remarkably, around the nodal lines, the supercurrent rectification amplitude
exhibits three-fold structures with an alternating sign. We show that the
hexagonal pattern and the three-fold structure in the interband phase space
turn out to be dependent on the tunneling amplitude of each band. These
findings provide hallmarks of the supercurrent rectification which can be
potentially employed to unveil the occurrence of spin-singlet multiband
superconductivity with time-reversal symmetry breaking.
