Defect Formation in NaI Crystals: A Novel Pathway to Dark Matter Detection

TL;DR

This paper explores how defect formation in NaI crystals caused by dark matter interactions could serve as a new detection method, using simulations to analyze defect properties and electronic states.

Contribution

It introduces a novel detection channel based on dark matter-induced defects in NaI crystals, supported by molecular dynamics and density functional theory analyses.

Findings

Defects can create new electronic states within the band gap.

Dark matter interactions can induce detectable defects in NaI.

Potential for defect-based dark matter detection methods.

Abstract

Sodium iodide (NaI) is a widely used scintillator in direct dark matter searches. In particular, NaI-based cryogenic scintillating calorimeters have emerged as promising candidates, like in the COSINUS experiment, for testing the annually modulating signal reported by DAMA/LIBRA. In this study, we investigate defect formation within NaI crystals and its impact on the dark matter detection signal. Using molecular dynamics simulations and density functional theory techniques, we simulate a DM particle collision on an NaI crystal, focusing on the possible defects formation and their structural and electronic properties. Our analysis includes a detailed study of the electronic states associated with the interstitial atoms and vacancies, the energetic cost of defect formation, and the anisotropic threshold displacement energy. Finally, we highlight the potential to exploit dark matter-induced defects as a novel detection channel, enabled by the introduction of new states within the electronic band gap.