3,585 research outputs found

    Interaction-dependent enhancement of the localisation length for two interacting particles in a one-dimensional random potential

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    We present calculations of the localisation length, λ2\lambda_{2}, for two interacting particles (TIP) in a one-dimensional random potential, presenting its dependence on disorder, interaction strength UU and system size. λ2(U)\lambda_{2}(U) is computed by a decimation method from the decay of the Green function along the diagonal of finite samples. Infinite sample size estimates ξ2(U)\xi_{2}(U) are obtained by finite-size scaling. For U=0 we reproduce approximately the well-known dependence of the one-particle localisation length on disorder while for finite UU, we find that ξ2(U)∼ξ2(0)β(U) \xi_{2}(U) \sim \xi_2(0)^{\beta(U)} with β(U)\beta(U) varying between β(0)=1\beta(0)=1 and β(1)≈1.5\beta(1) \approx 1.5. We test the validity of various other proposed fit functions and also study the problem of TIP in two different random potentials corresponding to interacting electron-hole pairs. As a check of our method and data, we also reproduce well-known results for the two-dimensional Anderson model without interaction.Comment: 34 RevTeX 3.0 pages with 16 figures include

    L\'{e}vy flights in quantum transport in quasi-ballistic wires

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    Conductance fluctuations, localization and statistics of Lyapunov exponents are studied numerically in pure metallic wires with rough boundaries (quasi-ballistic wires). We find that the correlation energy of conductance fluctuations scales anomalously with the sample dimensions, indicating the role of L\'{e}vy flights. Application of a magnetic field deflects the L\'{e}vy flights which reduces the localization length. This deflection also breaks the geometrical flux cancellation and restores the usual Aharonov-Bohm type magneto-conductance fluctuations.Comment: Available also at http://roberto.fis.uniroma3.it/leadbeat/pub.htm

    Non-linear conductivity and quantum interference in disordered metals

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    We report on a novel non-linear electric field effect in the conductivity of disordered conductors. We find that an electric field gives rise to dephasing in the particle-hole channel, which depresses the interference effects due to disorder and interaction and leads to a non-linear conductivity. This non-linear effect introduces a field dependent temperature scale TET_E and provides a microscopic mechanism for electric field scaling at the metal-insulator transition. We also study the magnetic field dependence of the non-linear conductivity and suggest possible ways to experimentally verify our predictions. These effects offer a new probe to test the role of quantum interference at the metal-insulator transition in disordered conductors.Comment: 5 pages, 3 figure

    Natural product biosynthesis: mechanistic and enzymatic studies

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