Detecting axion dynamics on the surface of magnetic topological insulators

Abstract

Axions, initially proposed to solve the strong CP problem, have recently gained attention in condensed matter physics, particularly in topological insulators. However, detecting axion dynamics has proven challenging, with no experimental confirmations to date. In this study, we identify the surface of magnetic topological insulators as an ideal platform for observing axion dynamics. The vanishing bulk gap at the surface allows for order $O(1)$ variations in the axion field, making the detection of axion-like phenomena more feasible. In contrast, these phenomena are strongly suppressed in the bulk due to the small magnetic exchange gap. We investigate two-photon decay as a signature of axion dynamics and calculate the branching ratio using a perturbative approach. Our findings reveal that the photon flux emitted from the surface is in-plane and orders of magnitude larger than that from the bulk, making it detectable with modern microwave technology. We also discuss potential material platforms for detecting axion two-photon decay and strategies to enhance the signal-to-noise ratio.

5+7 pages, 3+1 figures

References in corpus (6)

• Topological Field Theory of Time-Reversal Invariant Insulators
• Axion Electrodynamics in Topological Materials
• Magnetic imaging of antiferromagnetic domain walls
• Axion optical induction of antiferromagnetic order
• Origins of electronic bands in antiferromagnetic topological insulator MnBi${}_2$Te${}_4$
• Signature of band inversion in the antiferromagnetic phase of axion insulator candidate EuIn2As2

Cited by in corpus (1)

• Probing dynamical axion quasiparticles with two-photon correlations