  Perfect crossed Andreev reflection (CAR) is striking for high-efficiency
Cooper pair splitting which bears promising applications in quantum
communication. Recent experimental advances have disclosed the way to explore
CAR in Dirac fermion systems under ultra-strong magnetic fields. We develop a
scattering approach to study quantum Hall-superconductor-quantum Hall (QH-S-QH)
junctions formed by a two-dimensional (2D) time-reversal symmetric Dirac
semimetal. We propose two different setups of the hybrid junction in the
quantum limit where only zeroth Landau levels are involved in transport to
exploit perfect CAR. In both setups, the CAR probability can reach unity
without applying bias voltage and is controllable by the magnetic field
strength, junction width, length and doping of the superconductor. CAR
dominates the nonlocal transport and is directly measurable by the differential
conductances. We also identify a quantized spin injection per CAR event in one
of the two setups. Our proposal is experimentally feasible and will be helpful
for exploring high-efficiency Cooper pair splitting and spin injection in Dirac
materials.
