Spin conductivity spectrum in ultracold atomic gases

In this talk, we propose the method to measure frequency-dependent spin conductivity, which is elusive in solid-state materials [1]. Then, we present our theoretical analysis of the spin conductivity for several cold atomic systems in order to demonstrate that the spin conductivity spectrum becomes powerful probes to investigate many-body properteis of cold atoms. Indeed, the spin conductivity spectra includes physical information such as the Tomonaga-Luttinger parameter of spin in one-dimensional systems [1], topological phase transition in the 1D p-wave Fermi superfluid [2], and spin superfluidity in a binary Bose mixture [3].