Extended Data Fig. 2: Magnetic-field-dependent PL measurements of device A.

a, Evolution of the PL signal with n at B = 0 T. Cusps corresponding to ICI and FCI states at filling factors ν = −1 and ν = −2/3 are clearly visible. b,c, Evolution of the central energy of a non-dispersive Lorentzian fit to the trion peak in the PL signal with n for B ≥ 0 up to 7 T (b) and B ≤ 0 down to −7 T (c). The grey lines are guides for the eye following the B-dependent cusps and the colour of the line at a fixed B matches that of the corresponding dots in d and e. d,e, Evolution of the cusp charge density with magnetic field for the ICI state at ν = −1 (d) and the FCI state at ν = −2/3 (e). The cusp position for each B was determined using the maximum of the first derivatives of the peak energy with respect to n. The Chern numbers extracted on the basis of the fitted Streda formula at ν = −1 yield C = −1.01 ± 0.05 and C = 0.94 ± 0.08 for ν = −1 at positive and negative B, respectively. At ν = −2/3, the determined Chern numbers are C = −0.63 ± 0.06 (B ≥ 0) and C = 0.62 ± 0.04 (B ≤ 0).