Using bicircular light to design electronic symmetry and topology

vector potential — (a) Vector potential of bicircular light with frequency ratio of two traces out three-fold rose pattern. Relative phase 𝛼α between the two light components dictates overall rotation and the resulting light-induced symmetry lowering. (b) Light-induced breaking of inversion and time-reversal isolates single Weyl cones in energy momentum space. (c) Changing 𝛼α moves Weyl nodes in energy and momentum, with possibility for braiding. (d, e) Light-tunable gyrotropic magnetic effect, where electric currents are induced by an external magnetic field. The energy splitting of the Weyl nodes in panel (d) controls the amplitude an electric current 𝐽𝑧J_z proportional to an external magnetic field induced by the gyrotropic magnetic effect.

Irradiation of topological materials with intense bicircular light offers a versatile way to control bulk and surface states and transport on ultrafast timescales. When applied off-resonantly the light dresses the electronic states, which has direct consequences on the

band topology. The key idea is to use the unusual polarization state of bicircular light to selectively break symmetries, including spatial inversion. This opens the possibility to realize non centrosymmetric magnetic topological phases with unique chiral and/or polar properties. We identify Cd3As2 as a promising platform for bicircular Floquet engineering, since the topological low-energy manifold is well separated from trivial bands at higher energy. Using a realistic model, we predict a light-induced topological phase transitions into a non-centrosymmetric Weyl semimetal phase with isolated Weyl nodes. We also show that bicircular light can drive the system into a sought-after axion insulator state with exotic unpinned surface Dirac states that are protected by the combination of time-reversal and twofold rotation symmetry. Finally, we discover the dynamic gyrotropic magnetic effect, where bicircular light controls an electric current parallel to an external magnetic field via the movement of Weyl nodes in energy. This effect can serve as a smoking gun of the presence of isolated Weyl nodes.

“Bicircular Light Floquet Engineering of Magnetic Symmetry and Topology and Its Application to the Dirac Semimetal Cd3As2,” Thaís V. Trevisan, Pablo Villar Arribi, Olle Heinonen, Robert-Jan Slager, and Peter P. Orth, Phys. Rev. Lett. 128, 066602 (2022).

This research was supported by the Center for Advancement of Topological Semimetals, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, through the Ames Laboratory under Contract No. DE-AC02-07CH11358. R.-J. S. acknowledges funding from the Marie Skłodowska-Curie programme under EC Grant No. 842901 and the Winton program as well as Trinity College at the University of Cambridge.