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Abstract The giant circular photo‐galvanic effect is realized in chiral metals when illuminated by circularly polarized light. However, the structure itself is not switchable nor is the crystal chirality in the adjacent chiral domains. Here spindle‐shaped liquid crystalline elastomer microparticles that can switch from prolate to spherical to oblate reversibly upon heating above the nematic to isotropic transition temperature are synthesized. When arranged in a honeycomb lattice, the continuous shape change of the microparticles leads to lattice reconfiguration, from a right‐handed chiral state to an achiral one, then to a left‐handed chiral state, without breaking the translational symmetry. Accordingly, the sign of rotation of the polarized light passing through the lattices changes as measured by time‐domain terahertz spectroscopy. Further, it can locally alter the chirality in the adjacent domains using near‐infrared light illumination. The reconfigurable chiral microarrays will allow us to explore non‐trivial symmetry‐protected transport modes of topological lattices at the light–matter interface. Specifically, the ability to controllably create chiral states at the boundary of the achiral/chiral domains will lead to rich structures emerging from the interplay of symmetry and topology. 

Abstract This work focuses on the low frequency Drude response of bulk-insulating topological insulator (TI) Bi 2 Se 3 films. The frequency and field dependence of the mobility and carrier density are measured simultaneously via time-domain terahertz spectroscopy. These films are grown on buffer layers, capped by Se, and have been exposed in air for months. Under a magnetic field up to 7 Tesla, we observe prominent cyclotron resonances (CRs). We attribute the sharp CR to two different topological surface states from both surfaces of the films. The CR sharpens at high fields due to an electron-impurity scattering. By using magneto-terahertz spectroscopy, we confirm that these films are bulk-insulating, which paves the way to use intrinsic TIs without bulk carriers for applications including topological spintronics and quantum computing.