In-plane symmetry breaking induced tunable spin-dependent responses and polarization states for terahertz wave

•Our proposed tunable metamaterial focuses unconventionally on the in-plane rotation of meta-atoms.•The structural chirality is reconfigured by breaking the in-plane symmetries instead of the out-of-plane symmetries.•Our proposed metamaterial integrated on the kirigami substrate is capable of off-on-off modulations of the chirality by continuous stretching.•Upon linear polarization illumination, the polarization state of transmitted wave can be dynamically controlled to achieve tunable polarization conversion.