Triplons, magnons, and spinons in a single quantum spin system: SeCuO3RemoveLuc Testa, Vinko Šurija, Krunoslav Prša, Paul Steffens, Martin Boehm, Philippe Bourges, Helmuth Berger, Bruce Normand, Henrik M. Rønnow, and Ivica ŽivkovićPhys. Rev. B 103, L020409 (2021)