Three-body physics under dissipative spin–orbit coupling

We study the trimer state in a three-body system, where two of the atoms are subject to Rashba-type spin–orbit coupling and spin-dependent loss while interacting spin-selectively with the third atom. The short-time conditional dynamics of the three-body system is effectively governed by a non-Hermitian Hamiltonian with an imaginary Zeeman field. Remarkably, the interplay of non-Hermitian single particle dispersion and the spin-selective interaction results in a Borromean state and an enlarged trimer phase. The stability of trimer state can be reflected by the imaginary part of trimer energy and the momentum distribution of trimer wave function. We also show the phase diagram of the three-body system under both real and imaginary Zeeman fields. Our results illustrate the interesting consequence of non-Hermitian spectral symmetry on the few-body level, which may be readily observable in current cold-atom experiments.