Hot electron cooling in InSb probed by ultrafast time-resolved terahertz cyclotron resonance

Measuring terahertz (THz) conductivity on an ultrafast time scale is excellent way to observe charge-carrier dynamics in semiconductors as a function of after photoexcitation. However, measurement alone cannot separate the effects recombination from effective mass changes charges cool and experience different regions electronic band structure. Here we present form time-resolved magneto-THz spectroscopy which allows us measure cyclotron picosecond scale. We demonstrate this technique by observing electron cooling technologically-significant narrow-bandgap semiconductor indium antimonide (InSb). A significant reduction 0.032$m_\mathrm{e}$ 0.017$m_\mathrm{e}$ observed first 200ps injecting hot electrons. Measurement InSb photo-injected density agrees well with conduction non-parabolicity predictions ab initio calculations quasiparticle