Chirality Switching in 1T-TaS₂ by Highly Charged Ion Irradiation

In layered materials, charge density waves can occur in distinct chiral phases, which can be switched. We use Xe⁸⁺ ions at a kinetic energy of 22.5 keV to switch the commensurate charge density wave chirality on the nanoscale in 1T-TaS₂ at 50 K. Changes in spectral weight, density of states, and band structure are monitored in situ by angle-resolved photoemission spectroscopy. We find that changes in the band structure are most pronounced at the charge density wave gaps and that chirality switches gradually with ion fluence, saturating to near-full handedness reversal at ≳4000 ions/μm². We discuss a scenario for ion-induced chiral switching within the framework of intense, spatially confined electronic excitations, which induce a phase transition and defect-stabilized grain boundaries.