Fig. 3

LL transitions of bulk states. a The real part of the optical conductivity Re σ _xx (ω) in several magnetic fields. For clarity the spectra are displaced from one another by 100 with the spectrum at B = 17.5 T shown at its actual value. b The energies of the observed transitions as a function of magnetic field. Symbols: data. Solid lines: fits to the data using Eq. (1) discussed in the text with Δ = 64.5 meV and v _F = 0.4 × 10⁶ m s⁻¹. The observed resonances can be assigned to LL transitions T _n , which is due to transitions LL_-(n−1)→LL _n and LL_-n →LL _n−1 for n > 1 and LL₋₀→LL₁ for n = 1. c Schematic of LLs of the bulk states. The arrows illustrate T₁–T₃ shown in b