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FIR transmission and resistively detected cyclotron resonances in InSb

We have developed an experimental setup to simultaneously acquire magneto-transmission spectra and measure the photoconductive response. The low-temperature ($T$=4.2 K) magneto-transmission data for weakly doped InSb in the frequency range 3-15 THz and magnetic fields up to 25 T, shows that the AC conductivity is governed by the classical Drude response. Moreover, the resulting light-induced voltage in this system, consisting of thermoelectric and resistive contributions, both contain features that are related to cyclotron resonances. The frequency dependence of this resonance is in good agreement with $\mathbf{k\cdot p}$ perturbation theory and corresponds to transitions between the first and second Landau level with spin-up electrons. The obtained effective mass $m^{*}(B=0)=0.014m_{e}$, is in line with the value extracted from magneto-transmission experiments. Additionally, we can observe evidence of a fluence-dependent metal-insulator transition in the thermoelectric signal, which suggest that the electronic system becomes less sensitive to the light at higher frequencies.