On the decay of three-body nuclear molecule states

Harvey Stephen Huber

Kailash Kumar, Robert T. Folk

Grant L. Schumacher, Jere T. Mäkinen, Yunpeng Ji +5 more

Fermionic systems with multiple internal states, such as quarks in quantum chromodynamics and nucleons in nuclear matter, are at the heart of some of the most complex quantum many-body problems. The stability of such many-body multi-component systems is crucial to understanding, for instance, baryon formation and the nuclear structure, but these problems are typically challenging to tackle theoretically. Versatile experimental platforms on which to study analogous problems are thus sought-after. Here, we create a uniform three-component Fermi gas with controllable polarization, and observe anomalous decay of the polarized gas, in which the loss rates of each component unexpectedly differ, contradicting generic assumptions of three-body losses in this system. We introduce a generalized three-body rate equation which captures the decay dynamics, but the underlying microscopic mechanism is unknown. Three-component Fermi gases represent a versatile platform for quantum simulation, including quantum chromodynamics-like physics, pairing and few-body effects. Here the authors demonstrate control of spin imbalances and an unexpected asymmetric decay due to different three-body losses for each component, and whose microscopic mechanism remains to be understood.

X. Du, Y. Zhang, John E. Thomas

We measure inelastic three-body and two-body collisional decay rates for a two-component Fermi gas of 6Li, which are highly suppressed by the Pauli exclusion principle. Our measurements are made in the BEC-BCS crossover regime, near the two-body collisional (Feshbach) resonance. At high temperature (energy) the data show a dominant three-body decay process, which is studied as a function of bias magnetic field. At low energy, the data show a coexistence of two-body and three-body decay processes near and below the Feshbach resonance. Below resonance, the observed two-body inelastic decay can arise from molecule-atom and molecule-molecule collisions. We suggest that at and above resonance, an effective two-body decay rate arises from collisions between atoms and correlated (Cooper) pairs that can exist at sufficiently low temperature.

惇 栗山

Lihong Zhou, Xiaoling Cui

Two-body dissipation usually gives rise to a complex interaction. Here we study the effect of two-body dissipation on few-body physics, including the fundamental two-body effective scattering and the three-body Efimov physics. By employing a two-channel model that incorporates the decay of closed-channel molecules (generating the two-body dissipation), we explicitly relate the real and imaginary part of the inverse scattering length (${a}_{s}^{\ensuremath{-}1}$) to closed-channel detuning and decay rate. In particular, we show that the imaginary part of ${a}_{s}^{\ensuremath{-}1}$ is given by the product of the molecule decay rate and the effective range. Such complex scattering length is found to generate an additional imaginary Coulomb potential when three atoms come close to each other, thereby suppressing the formation of trimer bound states and modifying the conventional discrete scaling in Efimov physics.