Bound exciton in CuGaS2

Birefringence of CuGa2S4 crystals

“…One can conclude from these data that the energetic interval between the V 1 and V 2 bands equals 83 meV, and the interval between V 2 and V 3 bands is of 17 meV. These results suggest that the energetic intervals between the valence bands at room temperature and at 10 K are different [15][16][17][18][19][20]. Apart from that, the symmetry of the V 2 and V 3 bands becomes Г 7 and Г 6 , respectively.…”

“…The isotropic point λ o1 revealed at 2.5012 eV corresponds to the energy of the longitudinal exciton Г 4 . It was shown previously [16][17][18][19][20][21][22] that an energy transfer occurs between the waves of the excitonic polaritons Г 4 and Г 5 in the neighborhood of resonances, i.e. at these wavelengths.…”

“…The upper valence band is of the Γ 7 V symmetry and the lower conduction band is of Γ 6 C symmetry. The excitonic states are formed when the condition ℏω = E C − E V is fulfilled [16][17][18][19][20][21][22].…”

“…The gradual change of the refractive index in the E⊥c polarization is due to the Г 6 -Г 6 transitions. Three excitonic series A, B and C are revealed in the CuGaS 2 crystals [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. The interaction of electrons from the conduction band Г 6 and holes from the valence band Г 6 is determined by the product of irreducible representations Г 1 × Г 6 × Г 7 = Г 3 + Г 4 + Г 5 .…”