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  Fons, P.; Rodenbach, P.; Mitrofanov, K.; Kolobov, A.; Tominaga, J.; Shayduk, R.; Giussani, A.; Calarco, R.; Hanke, M.; Riechert, H.; Simpson, R.; Hase, M.: Picosecond strain dynamics in Ge₂Sb₂Te₅ monitored by time-resolved x-ray diffraction. Physical Review B 90 (2014), p. 094305/1-6

10.1103/PhysRevB.90.094305
Open Access Version (externer Anbieter)

Abstract:
Coherent phonons (CPs) generated by laser pulses on the femtosecond scale have been proposed as a means to achieve ultrafast, nonthermal switching in phase-change materials such as Ge2Sb2Te5 (GST). Here we use ultrafast optical pump pulses to induce coherent acoustic phonons and stroboscopically measure the corresponding lattice distortions in GST using 100-ps x-ray pulses from the European Synchrotron Radiation Facility (ESRF) storage ring. A linear-chain model provides a good description of the observed changes in the diffraction signal; however, the magnitudes of the measured shifts are too large to be explained by thermal effects alone, implying the presence of excited-state effects in addition to temperature-driven expansion. The information on the movement of atoms during the excitation process can lead to greater insight into the possibilities of using CP-induced phase transitions in GST.