Temperature-dependent and pump-probe ellipsometric studies of TlInSe2

Temperature-dependent phase-modulated spectroscopic ellipsometry over the photon energies 1.5–5.5 eV and temperatures 300–400 K, as well as pump-probe single wavelength rotating-analyzer laser ellipsometry at photon energy 1.61 eV and pumping power-density up to 160 W/cm2 has been carried out on TlInSe2 that has a quasi one-dimensional crystalline structure and apparently undergoes an incommensurate phase transition with temperature. Refractive indices and extinction coefficients, as well as their variation with temperature and pumping power-density have been determined. The change of the surface profile under pumping has been disclosed. The reversibility of the effect has been confirmed by the dynamic reflectance examination. Obtained results are discussed in terms of thermal effects and incommensurate phase transition in TlInSe2. It is proposed that a giant thermo-elastic effect and a soliton wave formation are behind the observed reversible change of the surface profile.