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

Abstract

We present calculations of the localisation length, $λ_{2}$, for two interacting particles (TIP) in a one-dimensional random potential, presenting its dependence on disorder, interaction strength $U$ and system size. $λ_{2}(U)$ is computed by a decimation method from the decay of the Green function along the diagonal of finite samples. Infinite sample size estimates $ξ_{2}(U)$ 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 $U$, we find that $ ξ_{2}(U) \sim ξ_2(0)^{β(U)} $ with $β(U)$ varying between $β(0)=1$ and $β(1) \approx 1.5$. 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.