g -factors of conduction electrons and holes in B i2S e3 three-dimensional topological insulator

Bulk-related conduction electron spin resonance and conduction hole spin resonance were investigated in B i₂S e₃ , a three-dimensional topological insulator. Electrons in the conduction band and holes in the valence band both have spin ½. The effective g -factors for conduction electrons are equal to 27.3 ± 0.15 for magnetic field parallel to the c axis and 19.48 ± 0.07 for magnetic field perpendicular to the c axis, whereas for conduction holes 29.90 ± 0.09 for magnetic field parallel and 18.96 ± 0.04 for magnetic field perpendicular to the c axis, respectively. Nonparabolicity effects were not observed in the investigated low carrier concentration range, below 8 ×10¹⁷c m^-3 . Large g -factors, higher by an order of magnitude than the free electron value, are due to strong spin-orbit interactions in B i₂S e₃ . The striking similarity of the spin resonances due to conduction electrons and holes confirms the peculiar symmetry between the conduction and valence bands of B i₂S e₃ , both having similar effective masses and spin character.