Charge dynamics of the antiferromagnetically ordered Mott insulator

TL;DR

This paper investigates the charge dynamics in an antiferromagnetic Mott insulator using a slave-fermion approach, revealing how spin fluctuations influence charge excitations and optical properties.

Contribution

It introduces a self-consistent framework combining slave-fermion formulation and spin fluctuation effects to accurately describe charge dynamics in the Mott insulator.

Findings

Reproduces Hubbard bands and spectral-weight transfer.

Shows Mott gap renormalization due to holon-doublon interactions.

Links optical gap to the Mott gap through optical conductivity calculations.

Abstract

We study the charge dynamics of the half-filled Hubbard model on the square lattice at zero temperature. We employ a slave-fermion formulation in which the charge degrees of freedom are represented by fermionic holons and doublons and the bosonic spin degrees of freedom are assumed to be described by the antiferromagnetic Heisenberg model. The ground state has long-ranged magnetic (N\'eel) order and its Mott-insulating characteristics are the consequence of holon-doublon bound-state formation. Within this framework, we calculate the average double occupancy, the electron density of states, and the spectral function in the self-consistent Born approximation. The lower and upper Hubbard bands are reproduced, there is spectral-weight transfer into a coherent quasiparticle band at their lower edges, and the Mott gap, associated with holon-doublon binding, is renormalized due to the interactions of the holons and doublons with the magnons. We compute the zeros of the Green function at the chemical potential to discuss the Luttinger volume and show that the poles of the self-energy reflect the underlying quasiparticle dispersion with a spin-renormalized hopping parameter. Optical conductivity results relate the optical gap to the Mott gap of the insulating system. We conclude that a self-consistent treatment of the spin fluctuation effects on the charge degrees of freedom captures all the essential physics of the antiferromagnetic Mott-Hubbard insulator.