"Superdense materials in the nano scale" by Huu Nguyen Dat

Seminar by Huu Dat Nguyen, Laboratoire Hubert Curien

Abstract

Study of matter in new phases at extreme pressures and temperatures is of importance for
functional and material designs. It has been demonstrated that those extreme conditions (TPa,
105 K) can be generated in table-top laboratory using ultrashort laser pulses tightly focused
inside transparent solid under micro-explosion concepts [1–3]. The tight focusing of fs pulses
at μJ energy level inside a bulk of transparent material can deposit several MJ/cm3 energy
density within submicron volume [4–6], which is higher than strength (Young modulus) of any
solid material. The extreme pressures of several TPa result in formation of cavity (void)
surrounded by a shell of superdense/compressed material.
In this respect, the project proposes an innovative approach based on engineered beams to
create and characterise superdense structural packing in fused silica and related materials,
from high density vitreous phases to new crystalline forms (pyrite). The proposed nondiffractive
Bessel beams can surpass the amount of energy deposition which is inherently
limited by light scattering on free carriers in the conventional Gaussian beam configuration. It
thereby pushes thermodynamic non-equilibrium to record-high levels of pressures and
temperatures, lifting kinetic barriers for new polymorphs and polyamorphs. The project targets
space-time irradiation design, observation of structural dynamics, characterisation of material
phases and their mechanical assessment. Ultrafast pump-probe optical imaging is employed
with phase and amplitude sensitivity to identify material evolutions on ns-μs timescales. Highresolution
imaging is facilitated by synchronised low-coherence random lasing probes, a novel
speckle-free rapid (ns) illumination source. The structural arrangement of the novel phases in
submicron levels is investigated by TEM characterisation in isolated dense zones which are
prepared by FIB techniques. The project expects to achieve a new level of understanding of
structural transitions in extreme spatial and temporal scales. It potentially helps predicting
conditions for synthesis of novel material phases under extreme shock and non-equilibrium.
Insights into formation kinetics helps engineering materials with extraordinary mechanical
properties, derived from record-high pressures and rapid quenching evolutions. It is
additionally of a fundamental interest as marker in geophysical high-energy interactions.

Reference
1. S. Juodkazis, K. Nishimura, S. Tanaka, H. Misawa, E. G. Gamaly, B. Luther-Davies, L. Hallo, P. Nicolai, and V.
T. Tikhonchuk, "Laser-Induced Microexplosion Confined in the Bulk of a Sapphire Crystal: Evidence of
Multimegabar Pressures," Phys. Rev. Lett. 96(16), 166101 (2006).
2. E. N. Glezer and E. Mazur, "Ultrafast-laser driven micro-explosions in transparent materials," Appl. Phys. Lett.
71(7), 882–884 (1997).
3. E. G. Gamaly, S. Juodkazis, K. Nishimura, H. Misawa, B. Luther-Davies, L. Hallo, P. Nicolai, and V. T.
Tikhonchuk, "Laser-matter interaction in the bulk of a transparent solid: Confined microexplosion and void
formation," Phys. Rev. B 73(21), 214101 (2006).
4. A. E. Turrell, M. Sherlock, and S. J. Rose, "Ultrafast collisional ion heating by electrostatic shocks," Nat Commun
6(1), 8905 (2015).
5. S. J. Tracy, S. J. Turneaure, and T. S. Duffy, "In situ X-Ray Diffraction of Shock-Compressed Fused Silica,"
Phys. Rev. Lett. 120(13), 135702 (2018).
6. Y. Shen, S. B. Jester, T. Qi, and E. J. Reed, "Nanosecond homogeneous nucleation and crystal growth in shockcompressed
SiO2," Nature Mater 15(1), 60–65 (2016).

This seminar will be held in english