Fig. 2: Excitonic states in monolayer MoSe₂.

a The band configurations of A and B bright excitons in monolayer MoSe₂. The arrows denote the electron spin of the bands. The Fermi level reaches only the inner subbands in our experiment. b The internal energy levels of exciton and exciton polaron. c Magnetic-field-dependent PL maps of monolayer MoSe₂ plotted in arbitrary unit (a.u.) at zero gate voltage and temperature T = 4 K. The lower panel shows the cross-cut PL spectra at five different magnetic fields. The dashed lines highlight the exciton energy shifts. The PL intensity in 1.74–1.90 eV is magnified 300 times for clarity. d The diamagnetic energy shift of the A-exciton 1s, 2s, and 3s states (denoted by red, green, and blue circles, respectively) as a function of the magnetic field. The error bars represent the uncertainty in fitting the PL spectra with multiple Lorentzian functions. The lines are quadratic fits. The inset shows the root-mean-square exciton radii (r_ns) for the principal quantum number n = 1, 2, 3. \({r}_{2{{{{{\rm{s}}}}}}}\) and \({r}_{3{{{{{\rm{s}}}}}}}\) are extracted from the diamagnetic shifts. \({r}_{1{{{{{\rm{s}}}}}}}\) is obtained by a theoretical model and it matches the experimental value in ref. ²⁷.