Magnetic field-driven charge carrier dynamics and time-reversal symmetry breaking in individual TI/FM heterostructures (Bi2Se3/Ni80Fe20/p-Si, Bi2Te2Se/Ni80Fe20/p-Si, and TlBiSe2/Ni80Fe20/p-Si) via pump-probe spectroscopy

Abstract

We investigate the ultrafast dynamics of TI (Bi₂Se_3, Bi₂Te₂Se, and TlBiSe₂)/p-Si and TI/FM (Bi₂Se₃/Ni₈₀Fe₂₀/p-Si, Bi₂Te₂Se/Ni₈₀Fe₂₀/p-Si, and TlBiSe₂/Ni₈₀Fe₂₀/p-Si) films using time-resolved pump-probe spectroscopy. The ultrafast study reveals that the insertion of Ni₈₀Fe₂₀ in between the TI and p-Si layer leads to decrease in the charge carrier's life time via acceleration in the decay of charge carriers. In addition to this, the study of Bi₂Se₃/Ni₈₀Fe₂₀/p-Si, Bi₂Te₂Se/Ni₈₀Fe₂₀/p-Si, and TlBiSe₂/Ni₈₀Fe₂₀/p-Si films was also carried out under the absence and presence of an external magnetic field. Our study indicates significant broadening in ground state bleaching and excited state absorption on exposure to magnetic field, accompanied with a reduction in absorption intensity and a shift in spectral positions. It is also observed that, the carrier recombination rates are enhanced, and the carrier lifetime decreases in the presence of a magnetic field. These observations are attributed to Zeeman and Rashba spin-orbit effects, leading to electronic state splitting and an increase in the density of states. Our findings are corroborated with static magneto-optic Kerr effect (MOKE) measurements, indicating time-reversal symmetry breaking in topological insulators under the influence of magnetic field.