Figure 2. LL spectroscopy of Bi₂Se₃ and Sb₂Te₂Se.

Tunnelling spectroscopy showing the LLs of the TSS measured at a fixed location of (a) Bi₂Se₃ and (b) Sb₂Te₂Se surface at 1.5 K. The spectra were acquired at different B from 0 T to 11 T with an interval of 1 T and are offset vertically for clarity. The red lines mark the energies of the Dirac points. The data shown in a are the same data used in ref. 22. Measurement conditions of b: V_s=−100 mV, I_t=50 pA and V_mod=1.4 mV_rms. (c) Scaling analysis of E_n(B) based on the data of Sb₂Te₂Se shown in b and a comparison with that of Bi₂Se₃. The E_n values were obtained by fitting the LL spectra with multiple Lorentz functions. The black curves depict the fitting to the low-energy parts of the scaling relations.