skip to content
 

Materials Modelling Seminar

Professor Andrei Rode

Laser Physics Centre, Research School of Physics and Engineering, The Australian National University

Monday 10 June 2019, 11:00 - 12:00

Location: Goldsmiths 1 (0_017), Department of Materials Science & Metallurgy

Title: Material modification at Megabar pressures with ultrashort laser pulses

Abstract:

Ultrashort laser pulses focussed down to a micron-size spot subsurface of transparent materials can achieve energy densities on the order of MJ/cm3, resulting in solid-density plasma formation, followed by a microexplosion and shockwave compression of the surrounding substance.  Subsequent rapid quenching leads to the formation and preservation of novel non-equilibrium material states.  Reaching extreme pressures is of fundamental interest for the formation of new material phases, and  also for the study of the Warm Dense Matter, reproducing the state of the cores of planets in table-top laboratory experiments.

Ultrafast laser induced microexplosion in confined geometry has already demonstrated the potential to create and preserve new thermodynamically non-equilibrium state of matter such as bcc-Al [1] and two tetragonal phases of Si [2].  These new phases have been predicted to exist theoretically, but have never before observed in nature or in laboratory experiments.  In this talk I’ll present a new way for increasing the shock wave affected volume by using a micro-Bessel beam with a 100:1 aspect ratio [3,4]. The experimental results show an effective formation of voids when such a beam focused inside sapphire crystal, which is a clear indication of significantly increased efficiency of new phase formation when compared with the previous experiments with a Gaussian laser beam.  The results open up a new way for increasing the quantity of high-density/pressure phases and help to increase sensitivity in search of new phases using X-ray and electron diffraction analysis.

[1] A. Vailionis et al., Evidence of superdense aluminium synthesized by ultrafast microexplosion, Nat. Comm. 2, 445 (2011).
[2] L. Rapp et al., Experimental evidence of new tetragonal polymorphs of silicon formed through ultrafast laser-induced confined microexplosion, Nat. Comm. 6, 7555 (2015).
[3] L. Rapp et al., High aspect ratio micro-explosions in the bulk of sapphire generated by femtosecond Bessel beams, Sci. Rep. 6, 34286 (2016).
[4] E. G. Gamaly and A. V. Rode, Ultrafast re-structuring of the electronic landscape of transparent dielectrics: new material states (Die-Met), Appl. Phys. A 124, 278 (2018).
 

talks.cam : http://www.talks.cam.ac.uk/talk/index/126241

Latest news

The elements of life under pressure

1 July 2021

First-principles structure prediction sheds light on high-pressure compounds formed from carbon, hydrogen, nitrogen and oxygen.

AIRSS for battery cathode materials

15 June 2021

A team of researchers at Cambridge and University College London have developed a computational framework for battery cathode exploration based on ab initio random structure searching.

Anatase-like Grain Boundary Structure in Rutile Titanium Dioxide

30 April 2021

A collaboration between researchers at Cambridge and AIMR has shed light on grain boundary structures in titania.

Physics World Breakthrough of the Year finalists for 2020

17 December 2020

A paper coauthored by Chris Pickard and Bartomeu Monserrat has been selected as a Top 10 finalist in Physics World's breakthroughs of the year for 2020.

An upper limit for the speed of sound

17 November 2020

A collaboration involving Bartomeu Monserrat and Chris Pickard was featured on both the University website and the Department website .

New fellowships for Chuck

17 November 2020

Congratulations to Chuck Witt, who began recently as a Schmidt Science Fellow and as a Junior Research Fellow at Christ's College, Cambridge! The Schmidt award is intended to catalyze new research directions and...

Machine learning shows how hydrogen becomes a metal inside giant planets

10 September 2020

By combining machine learning and quantum mechanics, researchers have carried out simulations to discover how hydrogen becomes a metal under extreme pressures.