Observation of Structural Anisotropy and the Onset of Liquidlike Motion During the Nonthermal Melting of InSb

The melting dynamics of laser excited InSb have been studied with femtosecond x-ray diffraction. These measurements observe the delayed onset of diffusive atomic motion, signaling the appearance of liquidlike dynamics. They also demonstrate that the root-mean-squared displacement in the $[111]$ direction increases faster than in the $[110]$ direction after the first 500 fs. This structural anisotropy indicates that the initially generated fluid differs significantly from the equilibrium liquid.

Figure 1

Time dependent diffraction intensity for the (111) (△) and the (220) (○) reflections. Data collected with laser fluences of $130\mathrm{mJ}{\mathrm{cm}}^{-2}$ 2a and $50\mathrm{mJ}{\mathrm{cm}}^{-2}$ 2b.

Figure 2

Time dependent root-mean-square displacement for the (111) (△) and the (220) (○) reflections. Data collected with laser fluences of $130\mathrm{mJ}{\mathrm{cm}}^{-2}$ 2a and $50\mathrm{mJ}{\mathrm{cm}}^{-2}$ 2b.

Figure 3

Fluence dependence of the inertial root-mean-square displacement for the (111) (△) and the (220) (○) reflections.