Emergent ballistic transport of Bose-Fermi mixtures in one dimension

The degenerate Bose-Fermi (BF) mixtures in one dimension present a novel realization of two decoupled Luttinger liquids with bosonic and fermionic degrees of freedom at low temperatures. However, the transport properties of such decoupled Luttinger liquids of charges is little known. Here we report on the transport properties of one-dimensional (1D) BF mixtures with delta-function interactions. The initial state is set up as the semi-infinite halves of two 1D BF mixtures with different temperatures, joined together at the time t = 0 and the junction point x = 0. Using the Bethe ansatz solution, we first rigorously prove the existence of conserved charges for both the bosonic and fermionic degrees of freedom, preserving the Euler-type continuity equations. Applying generalized hydrodynamics, we then analytically obtain the distributions of the densities and currents of the local conserved quantities which solely depend on the ratio ξ = x/t. The left and right moving quasiparticle excitations of the two halves form multiple segmented light-cone hydrodynamics that display ballistic transport of the conserved charge densities and currents in different degrees of freedom. Such profiles reveal a novel dynamical separation of the two Luttinger liquids of fermionic and bosonic atoms in 1D. Our analytical results provide a deep understanding of the role of interaction and quantum statistical effects in quantum transport.