Terahertz transitions between Landau levels in graphene with different concentrations of electrons

Abstract

The probability of terahertz transitions between Landau levels for various magnetic fields at 4.2 K is calculated at different positions of Fermi levels corresponding to different concentrations of electrons. A resonant type magnetic field dependence of light absorption at fixed Fermi energy is demonstrated. Besides the ideal case of well-defined Landau levels with small broadening, the effects of resonance degradation due to big broadenings and big fluctuations of Fermi energy along the sample are demonstrated. The maximum values of light absorption coefficients and their resonance positions in magnetic field scale Bmax were studied in a wide range of Fermi energies from 0 up to 400 meV at frequency THz of the incident beam. The calculation shows that Bmax increases when Fermi energy grows, but there are regions of plateaus resulting in semiladder type of this dependence. The peak values of light absorption manifest a periodic-like dependence on Fermi energy with a huge change in value (in several orders), although the increase in average of maximum value of absorption with Fermi energy is also observed. The possibility to observe photoconductivity response due to photoinduced charge carriers by terahertz transitions between Landau levels is discussed.