Carbon-dioxide-like Skyrmion controlled by spin-orbit coupling in atomic-molecular Bose-Einstein condensates

Atomic-molecular Bose-Einstein condensates (BECs) offer brand new opportunities to revolutionize quantum gases and probe the variation of fundamental constants with unprecedented sensitivity. The recent realization of spin-orbit coupling (SOC) in BECs provides a new platform for exploring completely new phenomena unrealizable elsewhere. However, there is no study of SOC atomic-molecular BECs so far. Here, we find a novel way of creating a Rashba-Dresselhaus SOC in atomic-molecular BECs by combining the spin dependent photoassociation and Raman coupling, which can control the formation and distribution of a new type of topological excitation -- carbon-dioxide-like Skyrmion. This Skyrmion is formed by two half-Skyrmions of molecular BECs coupling with one Skyrmion of atomic BECs, where the two half-Skyrmions locates at both sides of one Skyrmion, which can be detected by measuring the vortices structures using the time-of-flight absorption imaging technique in real experiments.