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Sujet de stage / Master 2 Internship

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Taking up the challenge of the glass transition by optical manipulations of molecules

Contact: LADIEU Francois, , francois.ladieu@cea.fr, +33 1 69 08 72 49
Summary:
Is there a thermodynamically well-defined glassy phase, or on the contrary are the glasses always in some out of equilibrium states the relaxation time of which is so great that the system appears as a solid ? Here we will seek to realize a gedenken experiment recently proposed by theoretical physicists to answer this question
Possibility of continuation in PhD: Non
Deadline for application:29/09/2019

Full description:
Context

According to the Nobel Prize awardee P.W. Anderson “The deepest and most interesting unsolved problem in solid state theory is probably the nature of glass and the glass transition”. This sentence reflects the fact that we still do not know if glasses are a true thermodynamic phase of matter or, on the contrary, if they are just out of equilibrium liquids which have become too viscous to flow on human time scales. Finding the answer to this seemingly simple question is hampered by the fact that, when decreasing temperature, the relaxation time of glass forming liquids becomes so large that one cannot rely onto the experimental techniques used to evidence standard thermodynamic phase transitions (e.g. liquid/gas transition or liquid/crystal transition). By using a totally new approach we aim at unveiling the nature of the glass transition, which is of great importance both for fundamental physics and for applications, since glasses play an increasing role in modern technologies (e.g. in optical fibers for communications, in photovoltaic devices, or in airplanes fuselages).

Objectives

More precisely, we aim at building an experiment corresponding to the “ideal thought experiment” proposed recently by some theorists, so as to unveil the presence or the absence of a true thermodynamic glass transition. In this experiment a fraction of molecules, randomly chosen in space, is pinned and one monitors the response of the rest of the liquid: if this pinning of a small fraction of molecules changes the global dynamics of the liquid, this means unambiguously that an order was present before establishing the pinning field, even though the extremely complex nature of this order had made it impossible to evidence by standard experimental tools. The approach that we have conceived needs: i) to design the optically sensitive molecules; ii) to build an optical setup allowing the realize pinning in the well-chosen liquid; iii) to compare the experimental results to the theoretical predictions. The internship consists in working onto the building and the exploitation of this experiment.

Profile of the candidate.

This project is a collaboration gathering all the required expertise between physicists, chemists, and theoreticians working at CEA Saclay –near Paris- and in the University of Montpellier. The internship will mainly take place in the NIMBE/LIONS and SPEC/SPHYNX laboratories in the CEA center of Saclay. We are looking for a candidate who, by relying onto the expertise available in the laboratories, really wants to invest herself/himself onto this project by providing us his/her skills either in organics chemistry or in experimental physics (optics, diffusion setups either in our laboratory or in large facilities, and dielectric spectroscopy).
Laboratory
Tutor of the internship

 

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