Figure: Top two panels show a 2D slice of a gallium arsenide layer with electron position shown in yellow and the direction of their spin shown as red arrows for low (left panel) and high (right panel) temperature. Once the electrons are hot enough, they evaporate out of local traps (bottom panels) and homogeneously distribute throughout the material, evenly spreading the spin.
demonstrate that electron spin relaxation in GaAs in the proximity of a Fe/MgO
layer is dominated by interaction with an exchange-driven hyperfine field at
temperatures below 60 K. Temperature-dependent spin-resolved optical pump-probe
spectroscopy reveals a strong correlation of the electron spin relaxation with
carrier freeze out, in quantitative agreement with a theoretical interpretation
that at low temperatures the free carrier spin lifetime is dominated by
inhomogeneity in the local hyperfine field due to carrier localization. As the
regime of large nuclear inhomogeneity is accessible in these heterostructures
for magnetic fields long-standing and contentious dispute concerning the origin of spin relaxation
in GaAs at
low temperature when a magnetic field is present. Further, this improved fundamental
understanding clarifies the importance of future experiments probing the
time-dependent exchange interaction at a ferromagnet/semiconductor interface and its
consequences for spin dissipation and transport during spin pumping.