Doublon production in correlated materials by multiple ion impacts

TL;DR

This paper extends NEGF simulations to larger correlated systems to study how multiple ion impacts generate doublons, revealing dependencies on impact timing and location with improved computational efficiency.

Contribution

It introduces an advanced G1--G2 NEGF scheme for larger, longer simulations of ion impacts on correlated materials, enabling detailed analysis of doublon formation.

Findings

Doublon population increases with multiple ion impacts.

Doublon creation depends on impact timing and location.

Enhanced simulation speed allows larger system analysis.

Abstract

In a recent Letter [Balzer \textit{et al.}, Phys. Rev. Lett. \textbf{121}, 267602 (2018)] it was demonstrated that ions impacting a correlated graphene cluster can excite strongly nonequilibrium states. In particular, this can lead to an enhanced population of bound pairs of electrons with opposite spin -- doublons -- where the doublon number can be increased via multiple ion impacts. These predictions were made based on nonequilibrium Green functions (NEGF) simulations allowing for a time-dependent non-perturbative study of the energy loss of charged particles penetrating a strongly correlated system. Here we extend these simulations to larger clusters and longer simulation times, utilizing the recently developed G1--G2 scheme [Sch\"unzen \textit{et al.}, Phys. Rev. Lett. \textbf{124}, 076601 (2020)] which allows for a dramatic speedup of NEGF simulations. Furthermore, we investigate the dependence of the energy and doublon number on the time interval between ion impacts and on the impact point.