First Principles Calculation of Universal Conductance Fluctuation in Monatomic Metal Chains

Combining the non-equilibrium Green＇s function method and density functional theory, we provide a first-principle scheme to calculate the universal conductance fluctuation （UCF） in quasi one-dimensional monatomic chains subject to a magnetic field. Our results show that for these monatomic chains, the amplitude of the UCF is much smaller than the previous theoretical prediction for mesoscopic conductors by Lee et al. [Phys. Rev. Lett. 55 （1985） 1622; Phys. Rev. B 36 （1987） 1039] The reason is that the ergodic hypothesis fails in these nanowires due to the confinement of geometry. We ascribe the phenomenon to the flux-dependent density of states fluctuation.