Evidence from Photoluminescence for the Splitting of the $s$-Conduction Band of the Ferromagnetic Semiconductor ${\mathrm{CdCr}}_2$${\mathrm{Se}}_4$

Photoluminescence spectra from ${\mathrm{CdCr}}_2$ ${\mathrm{Se}}_4$ have been measured at low temperatures. When the temperature was lowered below 70 K, an extra peak was observed on the higher-energy side of the band-to-band luminescence transition. The energy difference between the two peaks was measured to be 3.5 meV. The emission was attributed to the transitions from the split $s$-conduction bands.