Towards Floquet-topological Insulators by Polarized Microwave Drive on Three-terminal Graphene Josephson Junctions

Topological insulators have found new extensions via synthetic dimensions, allowing designed properties and unconventional control over physical parameters. For example, Floquet engineering exploits the interaction between band replicas and induced many-body interactions [1,2], whereas Andreev bands in multiterminal Josephson junctions exhibit unusual symmetries and topologies [3,4]. While these systems have independently been shown to exhibit topological signatures, quantum devices with Floquet physics have been rare due to the detrimental heating from the required driving forces. Fortunately, the long-term stability of Floquet-Andreev bands in graphene-based Josephson junctions (GJJ) has been demonstrated in microwave frequencies [5], thus foreshadowing an ideal system to probe Floquet-Andreev dynamics. Here, we understand three-terminal GJJs as having two synthetic dimensions, each defined by the superconducting phases and driven by time-delayed microwaves to emulate polarization in the Floquet drive. The resulting Floquet-Andreev band has been predicted to have a non-trivial Chern number, presenting a topologically nontrivial quantum device entirely in their synthetic dimensions.

 

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[2] J. W. McIver, B. Schulte, Nat. Phys 16, 38 (2020).

[3] N. Pankratova, H. Lee, et al., Phys. Rev. X 10, 0311051 (2020).

[4] W. Jung, S. Jin, et al., Sci. Adv. 11, eads0342 (2025).

[5] S. Park, W. Lee, et al., Nature 603, 421 (2022).