| | | | | | | webmail : intra-extra| Accès VPN| Accès IST| Contact | Français

Headlines 2010

14-06-2010
C. Bartolacci1, M. Laroche1, H. Gilles1, S. Girard1, T. Robin2, B. Cadier2 et A. Buisson3

1Equipe Lasers, Instrumentation Optique et Applications (LIOA), CIMAP / ENSICAEN, 6 BLVD Maréchal Juin, 14050  Caen  cedex,

2 iXFiber,  rue Paul Sabatier,  22300  Lannion  ixfiber

3 Laboratoire CI-NAPS, Centre CYCERON, Boulevard Becquerel, 14052 Caen cedex

11-02-2010
S. Haessler, J. Caillat, W. Boutu, C. Giovanetti-Teixeira, T. Ruchon, T. Auguste, Z. Diveki, P. Breger, A. Maquet, B. Carré, R. Taïeb & P. Salières,

Visualizing the motion of electrons in matter requires both a spatial resolution at the Angstrom scale and a temporal resolution at the attosecond scale (1 as = 10-18 s). Such an "ultra-fast camera" opening a path towards "viewing the electrons" is demonstrated: it allows imaging molecular orbitals using the ultra-short attosecond emission from this orbital in an intense laser field. In a close collaboration, scientists from IRAMIS-SPAMLCPMR of the Univ. Paris 6 and from CNRS (UMR 7614) have shown, in experiments realized within the CEA-Saclay, the possibility of an "Attosecond-Angstrom" imaging in the case of the nitrogen molecule N2.

 

24-11-2010
C. Hrelescu, T. K. Sau, A. L. Rogach, F. Jäckel, G. Laurent, L. Douillard et F. Charra

In optics, the possibility to confine light below its natural wavelength is hampered by the longstanding barrier of the diffraction limit. Surface plasmons are electromagnetic surface waves coupled to free electrons at metal dielectric interfaces. They offer a unique opportunity for scaling down photonic devices to the nanometre range. Experiments carried out in the SPCSI have investigated the differences between the spatial and spectral signatures of metallic nano-objects whether they are observed in far field (observed with our eyes in a classic optical microscope) or in near-field (observed at subwavelength scale using a photoemission electron microscope PEEM). This investigation brings important fundamental results in the plasmonics research field for the scaling down of photonic devices to the nanometre range.

14-06-2010
C. Bartolacci1, M. Laroche1, H. Gilles1, S. Girard1, T. Robin2, B. Cadier2 et A. Buisson3

1Equipe Lasers, Instrumentation Optique et Applications (LIOA), CIMAP / ENSICAEN, 6 BLVD Maréchal Juin, 14050  Caen  cedex,

2 iXFiber,  rue Paul Sabatier,  22300  Lannion  ixfiber

3 Laboratoire CI-NAPS, Centre CYCERON, Boulevard Becquerel, 14052 Caen cedex

01-06-2010

(version française Version française)

The violation of J. Bell's inequalities with two spatially separated objects is often considered as the most prominent demonstration of the quantum nature of our world: the objects can be so intimately entangled that speaking of the state of each object loses its meaning even when they are far apart. The famous experiment by A. Aspect's team, in which the two objects were polarized light particles (photons), was a perfect demonstration of such a non local realism.

30-03-2010

(version française Version française)

Researchers in the Instability and Turbulence Group of IRAMIS-SPEC have succeeded in experimentally characterizing the non linear mechanical response of an amorphous granular media across the jamming transition. They have demonstrated that global rigidity sets in via the critical growth of a correlation length.

 (title figure: Desplacement Field in the vicinity of an intruder dragged through a dense granular medium)

 

                 

fig_0001

Illustration 1: Experimental Schematics. An intruder particle is dragged by a constant force through an assembly of grains..

 

Illustration 2: Phase diagram: Two transitions are observed; fluidification transition (curve) and Jamming transition (vertical line)

 

Need a grain of advice? We've got thousands! In this experiment by the Instability and Turbulence Group, a mono-layer assembly of amorphous grains are compressed in a horizontal vibrating cell (see figure 1) until it reaches its maximum density. A transition, so-called 'blocking transition (jamming)' then occurs [1,2], at which a global rigidity in the media is achieved via the dynamic percolation of force chains.

Raphaël Candelier (PhD thesis) and his colleagues have studied the subtle characteristics of such a transition by tracking one particle, "intruder," dragged at a constant force in a 2D granular media. A phase diagram has been established (figure 2), demonstrating the presence of a fluidization line, above which the "intruder" advances continuously (just as in a glassy liquid), and below which the intruder adopts an intermittent motion with a strong fluctuation enhancement close to the jamming transition.

Video clip showing the strongly non-linear response presenting spatio-temporal intermittency under the fluidization line.

The raw images of the grains are represented in the bottom section of the screen, while the upper section shows the treated image of the grains color coded according to their respective instantaneous speeds. One can clearly see that - very close to the jamming transition - the material « hesitates» between a very rigid state and a very fluid counterpart. Long-range reorganizations are also observed indicating the critical nature of the transition. The existence of scaling laws has been demonstrated quantitatively by a « crackling noise » type analysis.

This phenomenology, explored by an original experimental procedure described here, has recently been published in two journal articles [3,4].

16-03-2010
J. Scheibert, C. Guerra, F. Célarié, D. Dalmas and D. Bonamy

Depending on their fracture mode, materials are traditionally gathered into three distinct classes:

  • (i) ductile materials that like metals deform plastically before their fracture
  • (ii) quasi-brittle materials such as rock or concrete, where "non-visible" damage starts to accumulate through microcracking, up to coalescence that yields to catastrophic failure.
  • (iii) brittle materials like oxide or polymer glasses... that deform elastically up to their fracture. This occurs through the successive breaking of atomic bonds at the crack tip. 

Experiments performed at IRAMIS-SPCSI show that a given material may, depending on the crack velocity, belong to two of these categories: Plexiglas®, archetype of brittle material, is found to damage through the nucleation of microcracks like quasi-brittle materials, beyond a well defined crack speed.


04-03-2010
D. S. Inosov1, J. T. Park1, P. Bourges2, D. L. Sun1, Y. Sidis2, A. Schneidewind3,4, K. Hradil4,5, D.Haug1, C. T. Lin1, B. Keimer1, and V. Hinkov

1 Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany
2 Laboratoire Léon Brillouin, CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette, France
3 Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), TU München, D-85747 Garching, Germany

In March 2008, superconductivity at high critical temperature (Tc> 50K) was found in iron-arsenide compounds  [1] to the surprise of the scientific community. Indeed, the magnetic iron was rather regarded as an antagonist of superconductivity. Moreover, it is the first time that a so high critical temperature is reached without copper. Very like copper oxide superconductors, these new superconductors have a lamellar structure with layers of iron and "pnictures" (compounds of As, P. .., that are elements of the 15th column of the Mendeleyev table) which are interposed between plans of "charge reservoirs" (see figure). These materials also present a phase diagram similar to that of cuprates with, versus the doping concentration, an antiferromagnetic phase adjacent to the superconducting zone ( [2]).

15-02-2010
Chemists of DSV (CEA-Life science Division) and physicists of DSM (CEA-Matter science Division) specialists of Nuclear Magnetic Resonance (NMR) have developed a new solid state NMR apporach to measure long inter-atomic distances. Based on the use of tritium, the hydrogen isotope with the highest sensitivity to NMR, this technique allows the determination of the conformation of small molecules bounded to their biological receptors. This determination is essential to understand the action mode of these molecules and to design new drugs of simpler structure and easier to synthesize.
11-02-2010
S. Haessler, J. Caillat, W. Boutu, C. Giovanetti-Teixeira, T. Ruchon, T. Auguste, Z. Diveki, P. Breger, A. Maquet, B. Carré, R. Taïeb & P. Salières,

Visualizing the motion of electrons in matter requires both a spatial resolution at the Angstrom scale and a temporal resolution at the attosecond scale (1 as = 10-18 s). Such an "ultra-fast camera" opening a path towards "viewing the electrons" is demonstrated: it allows imaging molecular orbitals using the ultra-short attosecond emission from this orbital in an intense laser field. In a close collaboration, scientists from IRAMIS-SPAMLCPMR of the Univ. Paris 6 and from CNRS (UMR 7614) have shown, in experiments realized within the CEA-Saclay, the possibility of an "Attosecond-Angstrom" imaging in the case of the nitrogen molecule N2.

 

13-01-2010
P. Maillet*, C. Levard**, E. Larquet§, C. Mariet,* O. Spalla*, N. Menguy§, A. Masion**, E. Doelsch, J. Rose** et Antoine Thill*

Imogolites (OH)3Al2O3Si(OH) are natural minerals discovered in 1962 in Japanese volcanic soils. Their structure is similar to that of a carbon nanotube. They are made of a curved Gibbsite  sheet Al(OH)3  forming a nanotube of 2 nm in diameter. The tetrahedral silicon adsorbed inside the nanotube controls  its curvature. The diificulties to synthesized  large quantities of  this  mineral have indered the development of industrial applications. Recently a new synthetic process has allowed to circumvent this difficulty. Research are now performed  to better understand and control this new synthesis.

24-11-2010
C. Hrelescu, T. K. Sau, A. L. Rogach, F. Jäckel, G. Laurent, L. Douillard et F. Charra

In optics, the possibility to confine light below its natural wavelength is hampered by the longstanding barrier of the diffraction limit. Surface plasmons are electromagnetic surface waves coupled to free electrons at metal dielectric interfaces. They offer a unique opportunity for scaling down photonic devices to the nanometre range. Experiments carried out in the SPCSI have investigated the differences between the spatial and spectral signatures of metallic nano-objects whether they are observed in far field (observed with our eyes in a classic optical microscope) or in near-field (observed at subwavelength scale using a photoemission electron microscope PEEM). This investigation brings important fundamental results in the plasmonics research field for the scaling down of photonic devices to the nanometre range.

04-03-2010
D. S. Inosov1, J. T. Park1, P. Bourges2, D. L. Sun1, Y. Sidis2, A. Schneidewind3,4, K. Hradil4,5, D.Haug1, C. T. Lin1, B. Keimer1, and V. Hinkov

1 Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany
2 Laboratoire Léon Brillouin, CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette, France
3 Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), TU München, D-85747 Garching, Germany

In March 2008, superconductivity at high critical temperature (Tc> 50K) was found in iron-arsenide compounds  [1] to the surprise of the scientific community. Indeed, the magnetic iron was rather regarded as an antagonist of superconductivity. Moreover, it is the first time that a so high critical temperature is reached without copper. Very like copper oxide superconductors, these new superconductors have a lamellar structure with layers of iron and "pnictures" (compounds of As, P. .., that are elements of the 15th column of the Mendeleyev table) which are interposed between plans of "charge reservoirs" (see figure). These materials also present a phase diagram similar to that of cuprates with, versus the doping concentration, an antiferromagnetic phase adjacent to the superconducting zone ( [2]).

11-02-2010
S. Haessler, J. Caillat, W. Boutu, C. Giovanetti-Teixeira, T. Ruchon, T. Auguste, Z. Diveki, P. Breger, A. Maquet, B. Carré, R. Taïeb & P. Salières,

Visualizing the motion of electrons in matter requires both a spatial resolution at the Angstrom scale and a temporal resolution at the attosecond scale (1 as = 10-18 s). Such an "ultra-fast camera" opening a path towards "viewing the electrons" is demonstrated: it allows imaging molecular orbitals using the ultra-short attosecond emission from this orbital in an intense laser field. In a close collaboration, scientists from IRAMIS-SPAMLCPMR of the Univ. Paris 6 and from CNRS (UMR 7614) have shown, in experiments realized within the CEA-Saclay, the possibility of an "Attosecond-Angstrom" imaging in the case of the nitrogen molecule N2.

 

15-02-2010
Chemists of DSV (CEA-Life science Division) and physicists of DSM (CEA-Matter science Division) specialists of Nuclear Magnetic Resonance (NMR) have developed a new solid state NMR apporach to measure long inter-atomic distances. Based on the use of tritium, the hydrogen isotope with the highest sensitivity to NMR, this technique allows the determination of the conformation of small molecules bounded to their biological receptors. This determination is essential to understand the action mode of these molecules and to design new drugs of simpler structure and easier to synthesize.
13-01-2010
P. Maillet*, C. Levard**, E. Larquet§, C. Mariet,* O. Spalla*, N. Menguy§, A. Masion**, E. Doelsch, J. Rose** et Antoine Thill*

Imogolites (OH)3Al2O3Si(OH) are natural minerals discovered in 1962 in Japanese volcanic soils. Their structure is similar to that of a carbon nanotube. They are made of a curved Gibbsite  sheet Al(OH)3  forming a nanotube of 2 nm in diameter. The tetrahedral silicon adsorbed inside the nanotube controls  its curvature. The diificulties to synthesized  large quantities of  this  mineral have indered the development of industrial applications. Recently a new synthetic process has allowed to circumvent this difficulty. Research are now performed  to better understand and control this new synthesis.

30-03-2010

(version française Version française)

Researchers in the Instability and Turbulence Group of IRAMIS-SPEC have succeeded in experimentally characterizing the non linear mechanical response of an amorphous granular media across the jamming transition. They have demonstrated that global rigidity sets in via the critical growth of a correlation length.

 (title figure: Desplacement Field in the vicinity of an intruder dragged through a dense granular medium)

 

                 

fig_0001

Illustration 1: Experimental Schematics. An intruder particle is dragged by a constant force through an assembly of grains..

 

Illustration 2: Phase diagram: Two transitions are observed; fluidification transition (curve) and Jamming transition (vertical line)

 

Need a grain of advice? We've got thousands! In this experiment by the Instability and Turbulence Group, a mono-layer assembly of amorphous grains are compressed in a horizontal vibrating cell (see figure 1) until it reaches its maximum density. A transition, so-called 'blocking transition (jamming)' then occurs [1,2], at which a global rigidity in the media is achieved via the dynamic percolation of force chains.

Raphaël Candelier (PhD thesis) and his colleagues have studied the subtle characteristics of such a transition by tracking one particle, "intruder," dragged at a constant force in a 2D granular media. A phase diagram has been established (figure 2), demonstrating the presence of a fluidization line, above which the "intruder" advances continuously (just as in a glassy liquid), and below which the intruder adopts an intermittent motion with a strong fluctuation enhancement close to the jamming transition.

Video clip showing the strongly non-linear response presenting spatio-temporal intermittency under the fluidization line.

The raw images of the grains are represented in the bottom section of the screen, while the upper section shows the treated image of the grains color coded according to their respective instantaneous speeds. One can clearly see that - very close to the jamming transition - the material « hesitates» between a very rigid state and a very fluid counterpart. Long-range reorganizations are also observed indicating the critical nature of the transition. The existence of scaling laws has been demonstrated quantitatively by a « crackling noise » type analysis.

This phenomenology, explored by an original experimental procedure described here, has recently been published in two journal articles [3,4].

16-03-2010
J. Scheibert, C. Guerra, F. Célarié, D. Dalmas and D. Bonamy

Depending on their fracture mode, materials are traditionally gathered into three distinct classes:

  • (i) ductile materials that like metals deform plastically before their fracture
  • (ii) quasi-brittle materials such as rock or concrete, where "non-visible" damage starts to accumulate through microcracking, up to coalescence that yields to catastrophic failure.
  • (iii) brittle materials like oxide or polymer glasses... that deform elastically up to their fracture. This occurs through the successive breaking of atomic bonds at the crack tip. 

Experiments performed at IRAMIS-SPCSI show that a given material may, depending on the crack velocity, belong to two of these categories: Plexiglas®, archetype of brittle material, is found to damage through the nucleation of microcracks like quasi-brittle materials, beyond a well defined crack speed.


 

Retour en haut