报告人：勒芒大学 Vitalyi E. Gusev教授
报告题目：Laser Ultrasonics in High Pressure Research: from Measurements of Material Parameters towards Imaging of its Inhomogeneity and Structural Transitions
报告时间：12月8日上午10:00
报告地点：唐仲英楼A213
摘要
Knowledge of pressure-dependences of sound velocities and elastic moduli of liquids and solids and understanding of the material texturing, plastic deformation and convection with increasing pressure is of extreme importance for a few branches of natural sciences such as condensed matter physics, physics of the Earth, seismology and planetology, as well as for monitoring of earthquakes, tsunamis or nuclear weapons tests. Starting 2008 [1,2] lasers have been increasingly applied for the generation and detection of the bulk acoustic waves in the materials subjected to high pressures in diamond anvil cells (DAC). Until now it was demonstrated that subnanosecond [2], femtosecond [1] and picosecond [3] laser pulses can be applied for the generation of compression/dilatation and shear bulk acoustic waves and bulk acoustic waves skimming along the interfaces between different materials confined in a DAC. Optical monitoring of the propagation of these waves provides information on the sound velocities and sound attenuation in materials under high pressures.
More recently picosecond ultrasonic interferometry (PAI) was applied for imaging of material spatial inhomogeneity and texturing, revealing the characteristic features of its micro-crystallinity and their evolution following the variation of pressure [3]. The high spatial resolution of PAI technique allowed to reliably determine the fastest and the slowest sound velocity in a single crystal of cubic H2O ice and thus to evaluate existing equations of state [4]. These results were compared with ab initio calculations. It is suggested that the transition from molecular ice VII to ionic ice X occurs at much higher pressures than proposed earlier, probably above 80 GPa. Further the results of PAI experiments, revealing differences in spatial structuring of different materials under pressure [5], and also of the experiments, indicating that dominant contribution to hypersound attenuation in polycrystalline materials in a DAC could be caused by acoustic scattering and not by absorption, were reported. The recent observations are also suggesting that laser radiation applied for the generation and detection of the acoustic waves in a DAC can be simultaneously used to transform the tested material from one crystalline state/structure into another [6]. The occurrence of these transitions can be followed by PAI in time. Two-dimensional spatial imaging of the phase transition dynamics revealed the direction and the velocity of the phase front motion [6].
[1] F. Decremps, L. Belliard, B. Perrin, and M. Gauthier, Phys. Rev. Lett. 100, 035502 (2008). [2] N. Chigarev, P. Zinin, L-C. Ming, G. Amulele, A. Bulou, and V. Gusev, Appl. Phys. Lett. 93, 181905 (2008). [3] S. M. Nikitin, N. Chigarev, V. Tournat, A. Bulou, D. Gasteau, B. Castagnede, A. Zerr, and V. E. Gusev, Sci. Rep. 5, 9352 (2015). [4] M. Kuriakose, S. Raetz,Q. M. Hu, S. M. Nikitin, N. Chigarev, V. Tournat, A. Bulou, A. Lomonosov, P. Djemia, V. E. Gusev, and A. Zerr, Phys. Rev. B 96, 134122 (2017). [5] M. Kuriakose, S. Raetz, N. Chigarev, S. M. Nikitin, A. Bulou, D. Gasteau, V. Tournat, B. Castagnede, A. Zerr, and V. E. Gusev, Ultrasonics, 69, 201 (2016). [6] M. Kuriakose, N. Chigarev, S. Raetz, A. Bulou, V. Tournat, A. Zerr and V. E. Gusev, New J. Phys. 19, 053206 (2017).
