We investigate the nonequilibrium populations of Andreev bound states (ABSs) in ballistic graphene three-terminal Josephson junctions (JJs). Our measurements reveal periodic resistance oscillations as a function of the superconducting phase, which is modulated by the applied magnetic flux. Additionally, we observe several voltage-induced crossovers, where resistance oscillations alternate between minima and maxima at integer flux quanta, corresponding to 0 and $\pi$ phase shifts, respectively. We utilize a microscopic model for long ballistic Andreev interferometers, accounting for both perturbative and nonperturbative scattering processes. This model attributes the $0\text{−}\pi$ crossovers to phase-sensitive Andreev reflections (ARs), which convert normal current into ABSs with nonequilibrium populations. Our combined theoretical and experimental approach suggests that unconventional energy-phase relations, such as $\pi$-shifted ABSs, can be created in multiterminal JJs without relying on complex Cooper quartet or Floquet physics.

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• Andreev bound states
• Andreev reflection
• Coherence length
• Critical current
• Josephson effect
• Methods in superconductivity
• Proximity effect
• Superconducting phase transition
• Superconductors