Fig. 4: Particle–hole mixture of the in-gap states.

Bogoliubov angle θ_B of the in-gap states with different mean energies \(\bar{{\varepsilon }}=({{\varepsilon }}_{+}-{{\varepsilon }}_{-})/2\) normalized to their minimal energies ε_min. All error bars are standard deviations extracted from fitting the data; see Supplementary Note 2 for details. The dashed grey lines represent the expected relationship for Bogoliubov quasiparticles with an induced gap of Δ_ind = ε_min as derived from the effective Hamiltonian in equation (2) (see Methods for details). Inset, Bogoliubov quasiparticles are coherent combinations of electrons (filled circle) and holes (empty circle). The Bogoliubov angle θ_B of a quasiparticle quantifies the amount of particle–hole mixing.