Electronic transport in a randomly amplifying and absorbing chain

We study localization properties of a one-dimensional disordered system characterized by a random non-hermitean hamiltonian where both the randomness and the non-hermiticity arises in the local site-potential; its real part being ordered (fixed), and a random imaginary part implying the presence of either a random absorption or amplification at each site. The transmittance (forward scattering) decays exponentially in either case. In contrast to the disorder in the real part of the potential (Anderson localization), the transmittance with the disordered imaginary part may decay slower than that in the case of ordered imaginary part.Comment: 7 LaTex pages plus 2 PS figures; e-mail: [email protected]

Phase Distribution in a Disordered Chain and the Emergence of a Two-parameter Scaling in the Quasi-ballistic to the Mildly Localized Regime

We study the phase distribution of the complex reflection coefficient in different configurations as a disordered 1D system evolves in length, and its effect on the distribution of the 4-probe resistance $R_4$. The stationary ($L \to \infty$) phase distribution is almost always strongly non-uniform and is in general double-peaked with their separation decaying algebraically with growing disorder strength to finally give rise to a single narrow peak at infinitely strong disorder. Further in the length regime where the phase distribution still evolves with length (i.e., in the quasi-ballistic to the mildly localized regime), the phase distribution affects the distribution of the resistance in such a way as to make the mean and the variance of $log(1+R_4)$ diverge independently with length with different exponents. As $L \to \infty$, these two exponents become identical (unity). Obviously, these facts imply two relevant parameters for scaling in the quasi-ballistic to the mildly localized regime finally crossing over to one-parameter scaling in the strongly localized regime.Comment: 12 LaTeX pages plus 3 EPS figure

Does hybrid density functional theory predict a non-magnetic ground state for delta-Plutonium?

Hybrid density functionals, which replaces a fraction of density functional theory (DFT) exchange with exact Hartree-Fock (HF) exchange, have been used to study the structural, magnetic, and electronic properties of delta-Plutonium. The fractions of exact Hartree-Fock exchange used were 25%, 40%, and 55%. Compared to the pure PBE functional, the lattice constants expanded with respect to the experimental value when the PBE-HF hybrid functionals were applied. A non-magnetic ground state was realized for 55% HF contribution; otherwise the ground state was anti-ferromagnetic. The 5f electrons tend to exhibit slight delocalization or itinerancy for the pure PBE functional and well-defined localization for the hybrid functionals, with the degree of 5f electron localization increasing with the amount of HF exchange. Overall, the performance of the hybrid density functionals do not seem superior to pure density functionals for delta-Plutonium.Comment: 24 pages (double spaced), 5 figures, 1 tabl