How Light Makes Tiny Whirlpools in Materials
ORAL · Invited
Abstract
Brighter, steadier lasers have now allowed the reprogramming of materials on demand. In Floquet engineering, periodic light “dresses” electrons, creating new phenomena absent at equilibrium. Experiments have visualized light-made bands on topological insulators and induced a light-driven anomalous Hall effect in graphene [1], highlighting intensity, frequency, and polarization as key knobs. A newer lever is to shape the beam itself: vortex (twisted) light carries spin angular momentum (from circular polarization) and orbital angular momentum (from a corkscrew wavefront), adding spatial structure that can drive matter into novel, switchable states [2].
This talk presents a theory that describes the effects of irradiating the surface of a Dirac-like material with a monochromatic vortex beam. Using Floquet theory, we build a total angular-momentum operator that couples electrons and photons that is conserved only for circular polarization, enabling accurate computation of quasienergies and eigenstates. In the one-photon limit, the system maps onto an s-wave superfluid, predicting multiply quantized electronic vortices with characteristic Caroli–de Gennes–Matricon core levels; compact analytic expressions closely match full numerical simulations [3]. We then contrast these vortex-core states with topological edge states, track their evolution as polarization is tuned from circular to linear, and assess robustness to dilute impurities [4], illustrating how structuring light in time and space can write and control quantum textures for ultrafast, optically switchable electronic and topological devices.
[1] J. W. McIver, B. Schulte, F.-U. Stein, T. Matsuyama, G. Jotzu, G. Meier, and A. Cavalleri, Nat. Phys. 16, 38–41 (2020).
[2] Y. Shen, X. Wang, Z. Xie, C. Min, X. Fu, Q. Liu, M. Gong, and X. Yuan, Light Sci. Appl. 8, 90 (2019).
[3] L. I. Massaro, C. Meese, N. P. Sandler, and M. M. Asmar, Phys. Rev. B 111, 085402 (2025).
[4] T. Walsh, E. Caldwell, N. P. Sandler, and M. M. Asmar, in preparation.
This talk presents a theory that describes the effects of irradiating the surface of a Dirac-like material with a monochromatic vortex beam. Using Floquet theory, we build a total angular-momentum operator that couples electrons and photons that is conserved only for circular polarization, enabling accurate computation of quasienergies and eigenstates. In the one-photon limit, the system maps onto an s-wave superfluid, predicting multiply quantized electronic vortices with characteristic Caroli–de Gennes–Matricon core levels; compact analytic expressions closely match full numerical simulations [3]. We then contrast these vortex-core states with topological edge states, track their evolution as polarization is tuned from circular to linear, and assess robustness to dilute impurities [4], illustrating how structuring light in time and space can write and control quantum textures for ultrafast, optically switchable electronic and topological devices.
[1] J. W. McIver, B. Schulte, F.-U. Stein, T. Matsuyama, G. Jotzu, G. Meier, and A. Cavalleri, Nat. Phys. 16, 38–41 (2020).
[2] Y. Shen, X. Wang, Z. Xie, C. Min, X. Fu, Q. Liu, M. Gong, and X. Yuan, Light Sci. Appl. 8, 90 (2019).
[3] L. I. Massaro, C. Meese, N. P. Sandler, and M. M. Asmar, Phys. Rev. B 111, 085402 (2025).
[4] T. Walsh, E. Caldwell, N. P. Sandler, and M. M. Asmar, in preparation.
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Publication: [1] L. I. Massaro, C. Meese, N. P. Sandler, and M. M. Asmar, Phys. Rev. B 111, 085402 (2025).
[2] T. Walsh, E. Caldwell, N. P. Sandler, and M. M. Asmar, in preparation.
Presenters
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Mahmoud M. Asmar
Kennesaw State University
Authors
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Mahmoud M. Asmar
Kennesaw State University