  Thermoelectric effect is exploited to optimize the Cooper pair splitting
efficiency in a Y-shaped junction, which consists of two normal leads coupled
to an $s$-wave superconductor via double noninteracting quantum dots. Here,
utilizing temperature difference rather than bias voltage between the two
normal leads, and tuning the two dot levels such that the transmittance of
elastic cotunneling process is particle-hole symmetric, we find currents
flowing through the normal leads are totally contributed from the splitting of
Cooper pairs emitted from the superconductor. Such a unitary splitting
efficiency is significantly better than the efficiencies obtained in
experiments so far.
