First-principles Spin and Optical Properties of Vacancy Clusters in Lithium Fluoride

TL;DR

This study uses hybrid functional calculations to accurately predict the spin and optical properties of vacancy clusters in lithium fluoride, highlighting the method's reliability for polar materials relevant to quantum technologies.

Contribution

The paper demonstrates the effectiveness of hybrid functional calculations in predicting defect properties in lithium fluoride, with insights into parameter sensitivity and defect level positioning.

Findings

Certain defects show consistent optical properties across different hybrid functional parameters.

Parameters satisfying Koopman's theorem can vary significantly for different charge states.

Hybrid functional approach is validated for accurate defect property prediction in polar materials.

Abstract

Vacancy-cluster color centers in lithium fluoride have been studied in detail both theoretically and experimentally for over a century, giving rise to various applications in solid-state lasers, broadband photonic devices, and radiation dosimeters. These color centers are also attractive candidate platforms for applications in quantum information science, due to their spin properties and strong coupling to the crystal lattice, which allows their properties to be easily tuned. Here we present hybrid functional calculations of common vacancy defects in lithium fluoride, including their energetic, spin, and optical properties. We show that for a wide range of hybrid functional parameters tuned to match the experimental band gap, certain defects have little variation in their predicted optical properties. We further demonstrate that the parameters needed to satisfy the generalized Koopman's theorem and correctly position defect levels within the gap, can vary dramatically, even for different charge states of the same defect. Our work establishes the accuracy of the computationally lightweight hybrid-functional approach for predicting the optical and energetic properties of color centers in polar materials.