Observing femtosecond orbital dynamics in ultrafast Ge melting with time-resolved resonant X-ray scattering

Lee, H.; Ahn, J.Y.; Chun, S.H.; Cho, D.H.; Sung, D.; Jung, C.; Shin, J.; Hwang, J.; Ha, S.S.; Jang, H.; Cho, B.-G.; Kim, S.; Park, J.; Nam, D.; Eom, I.; Shim, J.H.; Noh, D.Y.; Ihm, Y.; Song, C.

doi:10.1107/S2052252523007935

Figure 4
Laser fluence dependence of the lattice and orbital reflection. (a) Temporal evolution of the (0 0 6) orbital-sensitive and (0 0 4) Bragg intensities compared for different laser fluences. The onset time of lattice disorder becomes shorter for increased laser fluence (marked by the arrows). Solid lines are obtained from fits to single exponential functions (see Section S6 of the supporting information for details). (b) Fluence dependence of the intensity enhancement in the orbital-sensitive reflection and of the lattice disorder time is obtained. The excited carrier density was estimated considering the linear absorption process for reference (see Section S7 of the supporting information for details). The solid line is a guide to the eye. The experimental guide line (gray solid line) is extended to 200 mJ cm⁻² by adapting reference data (open square point) reported in other work in a nonthermal melting regime (Sokolowski-Tinten et al., 2001

). Better consistency of the experimental results (gray square) with the TTMD (green squares and broken guideline) at low fluence and with the AIMD (red squares and broken guideline) at high fluence indicates the crossover from thermal-effect-dominated low-fluence kinetics to nonthermal lattice disorder at higher fluence. Error bars were obtained from the fits.

IUCrJ

Volume 10| Part 6| November 2023| Pages 700-707

ISSN: 2052-2525

https://doi.org/10.1107/S2052252523007935

PHYSICS | FELS

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