Fig. 4: Relative oscillator strength of weak transitions and Δ|N| = 0 transitions.
From: Unconventional valley-dependent optical selection rules and landau level mixing in bilayer graphene
a Photocurrent spectra in the vicinity of transition (−5 → 5) at D = 0.874 V/nm. Spectra at 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 4.8 T are shifted horizontally to the center, and vertically by multiples of 0.6. The contrast between the “strong” and “weak” transitions is negligible at low fields but is appreciable at high fields. At 4.8 T, weak transitions are negligible in the spectrum. b Spectra in the vicinity of transition (−5 → 5) at D = 0.874, 1.02, and 1.32 V/nm. The relative oscillator strength of weak transitions to strong transitions increases at higher D for the same magnetic field of 4 T. Even in the scenario where cyclotron energies are similar (1.32 V/nm & 4.5 T, and 0.874 V/nm & 4 T), the oscillator strength is still more concentrated in weak transitions at higher D. c Relative oscillator strength as a function of the cyclotron energy at D = 1.32 V/nm. Data in blue (red) represent the ratio between the oscillator strength in Δ|N| = 0 (Δ|N| = 0 & Δ|N| = ± 2) transition and the integrated oscillator strength. The relative oscillator strength in Δ|N| = 0 is proportional to 1/(C.E.)2, where C.E. is the cyclotron energy. A typical energy scale of LL mixing ~1.8 meV can be extracted from this plot.
