Controlling absorption spectra of strained graphene nanoribbon by magnetic modulation

This study shows that the optical absorption spectra of strained graphene nanoribbons can be effectively tuned by a spatially modulated magnetic field. The absorption spectra exhibit many asymmetric square-root divergent peaks structure due to the oscillatory parabolic subbands. These absorption peaks can be classified into primary and secondary ones. The number, spectral intensity, and frequency of the absorption peaks depend sensitively on the strength and period of the modulated field. The transition channels of the absorption peaks are identified and the optical selection rule is analyzed. There exists an optical selection rule for the primary absorption peaks. Such rule is originated from the orthogonal properties of the quasi-Landau level wave functions. A uniaxial stress changes the band-edge state energy and subband curvature, in turn modifying the optical absorption spectra. The evolution of the frequencies of the absorption peaks with the field strength is explored. They first show linear, then square-root dependence on the field strength. These theoretical predictions can be validated by absorption spectroscopy experiments.