The generalized Lyapunov exponent for the one-dimensional Schrödinger equation with Cauchy disorder: some exact results

Abstract

We consider the one-dimensional Schrödinger equation with a random potential and study the cumulant generating function of the logarithm of the wave function $\psi (x)$, known in the literature as the "generalized Lyapunov exponent"; this is tantamount to studying the statistics of the so-called "finite size Lyapunov exponent". The problem reduces to that of finding the leading eigenvalue of a certain non-random non-self-adjoint linear operator defined on a somewhat unusual space of functions. We focus on the case of Cauchy disorder, for which we derive a secular equation for the generalized Lyapunov exponent. Analytical expressions for the first four cumulants of $\ln |\psi (x)|$ for arbitrary energy and disorder are deduced. In the universal (weak-disorder/high-energy) regime, we obtain simple asymptotic expressions for the generalized Lyapunov exponent and for all the cumulants. The large deviation function controlling the distribution of $\ln |\psi (x)|$ is also obtained in several limits. As an application, we show that, for a disordered region of size $L$, the distribution ${\mathcal{W}}_L$ of the conductance $g$ exhibits the power law behaviour ${\mathcal{W}}_L(g)\sim g^{-1/2}$ as $g\to 0$.

RevTex, 20 pages, 6 pdf figures

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Cited by in corpus (1)

• Disordered harmonic chain with random masses and springs: a combinatorial approach