Logarithmic current fluctuations in nonequilibrium quantum spin chains
Logarithmic current fluctuations in nonequilibrium quantum spin chains
We study zero-temperature quantum spin chains, which are characterized by a nonvanishing current. For the $XX$ model starting from the initial state \ensuremath{\mid}\ensuremath{\cdots}\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\downarrow}\ensuremath{\downarrow}\ensuremath{\cdots}⟩ we derive an exact expression for the variance of the total spin current. We show that asymptotically the variance exhibits an anomalously slow logarithmic growth; we also …