title: Transport in the XX chain at zero temperature: emergence of flat magnetization profiles.
abstract: We study the connection between magnetization transport and magnetization profiles in zero-temperature XX chains. The time evolution of the transverse magnetization m(x,t) is calculated using an inhomogeneous initial state that is the ground state at fixed magnetization but with m reversed from -m(0) for x<0 to m(0) for x>0. In the long-time limit, the magnetization evolves into a scaling form m(x,t)=Phi(x/t) and the profile develops a flat part (m=Phi=0) in the (x/t)<or=c(m(0)) region. The flat region shrinks to zero if m(0)-->1/2 while it expands with the maximum velocity c(0)=1 for m(0)-->0. The states emerging in the scaling limit are compared to those of a homogeneous system where the same magnetization current is driven by a bulk field, and we find that the expectation values of various quantities (energy, occupation number in the fermionic representation) agree in the two systems.
authors.affiliation: Institute for Theoretical Physics, Eötvös University, Pázmány sétány 1/a, 1117 Budapest, Hungary.
authors.forename: T
authors.initials: T
authors.lastname: Antal
authors.forename: Z
authors.initials: Z
authors.lastname: Rácz
authors.forename: A
authors.initials: A
authors.lastname: Rákos
authors.forename: G M
authors.initials: GM
authors.lastname: Schütz