Phase protection of Fano-Feshbach resonances.

Decay of bound states due to coupling with free particle states is a general phenomenon occurring at energy scales from MeV in nuclear physics to peV in ultracold atomic gases. Such a coupling gives rise to Fano-Feshbach resonances (FFR) that have become key to understanding and controlling interactions-in ultracold atomic gases, but also between quasiparticles, such as microcavity polaritons. Their energy positions were shown to follow quantum chaotic statistics. In contrast, their lifetimes have so far escaped a similarly comprehensive understanding. Here, we show that bound states, despite being resonantly coupled to a scattering state, become protected from decay whenever the relative phase is a multiple of π. We observe this phenomenon by measuring lifetimes spanning four orders of magnitude for FFR of spin-orbit excited molecular ions with merged beam and electrostatic trap experiments. Our results provide a blueprint for identifying naturally long-lived states in a decaying quantum system.

Citation

Alexander Blech, Yuval Shagam, Nicolas Hölsch, Prerna Paliwal, Wojciech Skomorowski, John W Rosenberg, Natan Bibelnik, Oded Heber, Daniel M Reich, Edvardas Narevicius, Christiane P Koch. Phase protection of Fano-Feshbach resonances. Nature communications. 2020 Feb 21;11(1):999

PMID: 32081896

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