Floquet-Bloch manipulation of correlated topological materials

Emergent phases, the physics of strongly interacting particles, have proven fertile ground for novel condensed matter physics. These phases manifest as collective modes such as charge density waves and superconductivity and global ordering such as ferromagnetism and topological ordering. Modification of topological order by symmetries broken due to strongly correlated order has led to observation of the quantum anomalous Hall effect in magnetically-order topological insulators and the proposition of Kramers-Weyl fermions in chiral topological semi-metals. In this work, we use helicity-dependent ARPES to suggest the presence of such nodes in the quasi-1D topological semi-metal (TaSe4)2I. Time- and angle-resolved photoemission spectroscopy is an ideal tool to probe strongly correlated topological materials. The surface sensitivity of spectroscopic probes has proven critical to the observation of topological states, such as the Dirac fermions of a 3D topological insulator. Indications of charge density wave order, like band folding and lifted degeneracies from magnetic order, are easily accessed by photoemission spectra. Time-resolved techniques operate by coherently exciting carriers and observing the resultant out-of-equilibrium phases such as phonons and excitons and other such collective modes. Control of material properties can, likewise, be achieved with time-resolved techniques. A time-periodic drive generated from a strongly pulsed laser field can be used to generate Floquet-Bloch states. These hybrid photon-electron states produce states replicated in energy and momentum. This coherent driving is capable of inducing, and thus optically controlling, topological phases transitions, and for uncovering properties of materials that may elude conventional probes. The application of Floquet-Bloch manipulation in magnetically-ordered topological systems remains under-explored. In this work we realize Floquet-Bloch manipulation of the Dirac surface-state mass of the topological antiferromagnet MnBi2Te4. We show that coherently driving this system with opposite helicities of mid-infrared circularly-polarized light results in substantially different Dirac mass gaps in the antiferromagnetic phase, despite the equilibrium Dirac cone appearing massless. Via Floquet-Bloch manipulation we reveal a Dirac mass gap obscured by magnetic disorder on the surface of MnBi2Te4.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Bielinski, Nina

Contributors dc:contributor

• Mahmood, Fahad
• Madhavan, Vidya
• Hughes, Taylor
• Shoemaker, Daniel

• condensed matter
• quantum materials
• magnetism
• topological materials
• correlated materials
• floquet
• ARPES
• ultrafast spectroscopy

Statement dc:rights

• 2025 Nina Bielinski

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129391

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129391