Low-energy excitations of one dimensional (1D) interacting fermions typically split into two coherent  Tomonaga-Luttinger liquid (TLLs), each of which carries either spin  or charge. This phenomenon is called spin-charge separation--a hallmark of 1D many-body physics. Although there have been more than 40 years of research in this field, theoretical understanding and definite experimental observation of this phenomenon are still challenging. 

In this talk, I will report on our recent precise observation of  the TLL theory of spin-charge separation in the trapped 1D ultracold Fermi gas.  This work, for the first time, experimentally verifies the TLL theory of the spin-charge separation and provides strong evidence for nonlinear TLL effects, beyond the linear TLL model. It is a paradigmatic example of quantum many-body physics, offers new insight into quantum physics. (References: Phys. Rev. Lett. 125,190401 (2020); Science，376, 1305(2022)).