Exact numerical methods for a many-body Wannier Stark system

TL;DR

This paper introduces exact numerical methods using Lanczos diagonalization for analyzing many-body Wannier-Stark systems with two Bloch bands, enabling efficient study of complex quantum dynamics and spectral features.

Contribution

The paper develops ab initio, exact numerical techniques employing Lanczos algorithms for large sparse matrices to analyze many-body Wannier-Stark systems with strong interactions.

Findings

Polynomial scaling of computational time with system size

Efficient detection and analysis of avoided crossings

Comparison showing Lanczos is more efficient than Runge-Kutta for time evolution

Abstract

We present exact methods for the numerical integration of the Wannier-Stark system in a many-body scenario including two Bloch bands. Our ab initio approaches allow for the treatment of a few-body problem with bosonic statistics and strong interparticle interaction. The numerical implementation is based on the Lanczos algorithm for the diagonalization of large, but sparse symmetric Floquet matrices. We analyze the scheme efficiency in terms of the computational time, which is shown to scale polynomially with the size of the system. The numerically computed eigensystem is applied to the analysis of the Floquet Hamiltonian describing our problem. We show that this allows, for instance, for the efficient detection and characterization of avoided crossings and their statistical analysis. We finally compare the efficiency of our Lanczos diagonalization for computing the temporal evolution of our many-body system with an explicit fourth order Runge-Kutta integration. Both implementations heavily exploit efficient matrix-vector multiplication schemes. Our results should permit an extrapolation of the applicability of exact methods to increasing sizes of generic many-body quantum problems with bosonic statistics.