Illustration from Scientific Research

Spin-exchange CM (SE-CM) in Mn-doped PbSe QDs. Spin directions are shown by short, black single-sided arrows. Spin-conserving transitions are shown by red arrows. Due to spin conservation, the biexciton produced via relaxation of the excited Mn ion is a combination of a dark and a bright exciton (spins 1 and 0, respectively) in two different L valleys of PbSe (L 1 and L 2 ). The final biexciton state comprises two band-edge electrons with co-aligned spins, which is impossible in a single-valley semiconductor due to Pauli exclusion.

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