Ultrafast charge recombination in photoexcited Mott-Hubbard insulator

TL;DR

This paper models the rapid recombination of photoexcited holon-doublon pairs in Mott-Hubbard insulators, explaining ultrafast processes observed experimentally through multi-magnon emission mechanisms.

Contribution

It provides a quantitative explanation for ultrafast charge recombination in Mott insulators using a two-dimensional model and multi-magnon emission theory.

Findings

Recombination rate depends exponentially on Mott-Hubbard gap and magnon energy.

Fast decay observed in experiments can be explained by strong correlations and exciton-magnon coupling.

Existence of Mott-Hubbard bound exciton of s-type is crucial for the process.

Abstract

We present a calculation of the recombination rate of the excited holon-doublon pairs based on the two-dimensional model relevant for undoped cuprates which shows that fast processes, observed in pump-probe experiments on Mott-Hubbard insulators in picosecond range, can be explained even quantitatively with the multi-magnon emission. The precondition is the existence of the Mott-Hubbard bound exciton of the s-type. We find that its decay is exponentially dependent on the Mott-Hubbard gap and on the magnon energy, with a small prefactor which can be traced back to strong correlations and consequently large exciton-magnon coupling.