Effective creation of ultracold deeply-bound molecules via non-Hermitian stimulated Raman shortcut-to-adiabatic passage

In this paper, we carry out the non-Hermitian stimulated Raman shortcut-to-adiabatic passage (NH-STIRSAP) to create ultracold deeply-bound molecules. The open three-level molecular system is supposed to have irreversible decays out of all levels. Under the assumption of large single-photon detuning and/or strong loss rate of the excited level, the NH three-level system can be theoretically reduced to an effective two-level system. By continuously using the counter-diabatic driving of the shortcut-to-adiabaticity, an auxiliary field is produced to couple the Feshbach level with the ground level. In the numerical calculations, we firstly consider the case of decaying only from the excited level, which is the main loss of the system. Under the NH-STIRSAP, the calculations reveal that complete population transfer from the Feshbach to the ground level can occur even if the adiabatic condition is not fulfilled. Therefore, the creation efficiency of ultracold deeply-bound molecules is greatly improved. The results hold equally for counter-intuitive and intuitive time sequence of the Stokes and pump pulse. If the decays from the Feshbach and ground level are also included, the NH-STIRSAP can still restore most of that efficiency, which performs much better than typical stimulated Raman adiabatic passage. Finally, we point out that the robustness and fast transfer speed of the NH-STIRSAP facilitate the creation and detection of ultracold deeply-bound molecules. •The STIRSAP scheme is extended from closed system to open NH system.•The NH-STIRSAP is employed to create ultracold deeply-bound molecules.•Adiabatic elimination conditions of large single-photon detuning and/or strong loss rate of the excited state are used to help us designing the auxiliary field coupling the Feshbach and the ground state.•Compared with the common stimulated Raman adiabatic passage (STIRAP), high creation efficiency of ultracold deeply-bound molecules can still be obtained under the NH-STIRSAP even if the adiabatic condition is not fulfilled.•The transfer speed from weakly-bound to deeply-bound molecules is much faster under the NH-STIRSAP.•The creation and detection of ultracold deeply-bound molecules occurs regardless the pulse sequence of the pump and Stokes pulse, which allows minimizing the off-resonant scattering.