Revealing the hidden Dirac gap in a topological antiferromagnet using Floquet-Bloch manipulation

• DOI: 10.48550/arxiv.2405.16432
• Publication Date: 2024-01-01
• Authors: Bielinski, Nina; Chari, Rajas; May-Mann, Julian; Kim, Soyeun; Zwettler, Jack; Deng, Yujun; Aishwarya, Anuva; Roychowdhury, Sub...; Shekhar, Chandra; Hashimoto, Makoto; Lu, Donghui; Yan, Jiaqiang; Felser, Claudia; Madhavan, Vidya; Shen, Zhi-Xun; Hughes, Taylor L.; Mahmood, Fahad
• Keywords: Condensed Matter - Mesoscale and Nanoscale Physics; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); FOS: Physical sciences

Manipulating solids using the time-periodic drive of a laser pulse is a promising route to generate new phases of matter. Whether such `Floquet-Bloch' manipulation can be achieved in topological magnetic systems with disorder has so far been unclear. In this work, we realize Floquet-Bloch manipulation of the Dirac surface-state mass of the topological antiferromagnet (AFM) MnBi$_2$Te$_4$. Using time- and angle-resolved photoemission spectroscopy (tr-ARPES), we show that opposite helicities of mid-infrared circularly polarized light result in substantially different Dirac mass gaps in the AFM phase, despite the equilibrium Dirac cone being massless. We explain our findings in terms of a Dirac fermion with a random mass. Our results underscore Floquet-Bloch manipulation as a powerful tool for controlling topology even in the presence of disorder, and for uncovering properties of materials that may elude conventional probes.