# Large dynamical axion field in topological antiferromagnetic insulator Mn$_2$Bi$_2$Te$_5$

## TL;DR

This paper predicts that certain layered antiferromagnetic materials, specifically Mn$_2$Bi$_2$Te$_5$-related compounds, can host a dynamical axion field, which could be experimentally detected through optical and transport measurements.

## Contribution

The study combines analytic models and first-principles calculations to identify real materials capable of hosting a dynamical axion field with topological origin.

## Key findings

- Identification of Mn$_2$Bi$_2$Te$_5$-related materials as candidates for dynamical axion fields
- Large dynamical axion fields achievable near topological phase transitions
- Proposed experimental methods for detecting the dynamical axion field

## Abstract

The dynamical axion field is a new state of quantum matter where the magnetoelectric response couples strongly to its low-energy magnetic fluctuations. It is fundamentally different from an axion insulator with a static quantized magnetoelectric response. The dynamical axion field exhibits many exotic phenomena such as axionic polariton and axion instability. However, these effects have not been experimentally confirmed due to the lack of proper topological magnetic materials. Here by combining analytic models and first-principles calculations, we predict a series of van der Waal layered Mn$_2$Bi$_2$Te$_5$-related topological antiferromagnetic materials could host the long-sought dynamical axion field with a topological origin. We also show a large dynamical axion field can be achieved in antiferromagnetic insulating states close to the topological phase transition. We further propose the optical and transport experiments to detect such a dynamical axion field. Our results could directly aid and facilitate the search for topological-origin large dynamical axion field in realistic materials.