Light figure studies of optical anisotropy induced by nanoscale spatial modulation in TlInS2 Original Research Article

The incommensurate material, TlInS2, with layer structure was studied by light figure spectroscopy techniques in spectral range 400–700 nm in temperature interval 80–350 K. Evolution of light figures with temperature in phase transition region was reliably established. The optic angle of TlInS2 was found to be sample-dependent with essentially two types of critical behavior with temperature; peak-like behavior that was ascribed to a pure incommensurate phase and peak-free behavior that was attributed to the influence of the domains or defects. In latter case the samples showed symmetry forbidden rotation of optic plane with temperature. As a whole, the obtained results allow for a conclusion that incommensurate spatial modulation with correlation length at the nanoscale was contributing to biaxial anisotropy of TlInS2 to a level of 10−3 versus 10−4 for basic lattice.