Publications

2015

• New aspects of electronic excitations at the bismuth surface: Topology, thermalization and coupling to coherent phonons
  
  • Perfetti L
  • Faure Jérôme
  • Papalazarou E
  • Mauchain Julien
  • Marsi M
  • Taleb-Ibrahimi A
  • Ohtsubo Y
  Journal of Electron Spectroscopy and Related Phenomena, Elsevier, 2015. We review measurements of angle and time resolved photoelectron spectroscopy on the surface states of the Bi(1 1 1) surface. The work covers several aspects of these surface states, discussing the topological properties, the strong anisotropy of the spin–orbit splitting and the dynamical relaxation of photoexcited electrons. Since time resolved experiments disentagle interaction processes in real time, the reported data offer a novel perspective on the motion of charge carriers in surface states and will serve as an unuseful reference for other systems with strong spin–orbit coupling. (10.1016/j.elspec.2014.12.004)
  DOI : 10.1016/j.elspec.2014.12.004
• The effect of irradiation on the magnetic properties of rock and synthetic samples: Implications to irradiation of extraterrestrial materials in space
  
  • Bezaeva N.S.
  • Gattacceca J.
  • Rochette P.
  • Duprat J.
  • Rizza G.
  • Vernazza P.
  • Trukhin V.I.
  • Skripnik A.Y.
  Fizika zemli / Izvestiya Physics of the Solid Earth, MAIK Nauka/Interperiodica/Springer, 2015, 51 (issue 3), pp.336-353. We report here the results of laboratory analog experiments to consider the potential effects of solar energetic particles (SEP or solar-flare-associated particles) and galactic cosmic rays (GCR) on the magnetic properties of extraterrestrial materials. We carried out proton bombardment experiments (with irradiation energies E (1)=400, E (2) =850 keV and three irradiation fluences in 10(14)-10(16) p/cm(2) range) and lead-ion bombardment experiments (E =1 GeV) on (previously demagnetized by 120 mT alternating magnetic field) rock and synthetic samples with the following magnetic carriers: metallic iron and nickel iron, Ti-rich and Ti-free magnetite, pyrrhotite. Irradiation experiments resulted in either further demagnetization or magnetization of irradiated samples depending on the type of magnetic mineralogy and type of ionizing radiation involved. Apart for the formation of radiation-induced remanent magnetization (RIRM), we observed major changes in bulk magnetic properties, i.e., a moderate to dramatic decrease (up to 93%) in the coercivity of remanence B (cr) for all iron-bearing phases (iron-in-epoxy and Bensour meteorite samples). Contrary to iron-bearing samples, several magnetite-bearing samples experienced a radiation-induced magnetic hardening (increase in B (cr) ). Magnetic hardening was also observed for Ar2+ ion-irradiated nickel iron-bearing HED meteorites, measured for comparison with the previously stated results. Therefore, the combined effect of SEP with GCR may magnetically soften iron-bearing materials and harden magnetite-bearing materials. In order to answer the question wether RIRM may account for natural remanent magnetization of meteorites and lunar samples, physical mechanism of RIRM formation and potential dependence of RIRM intensity on the background magnetic field present during irradiation event should be investigated. (10.1134/S1069351315020019)
  DOI : 10.1134/S1069351315020019
• Nanosecond (ns) laser transfer of silver nanoparticles from silver-exchanged soda-lime glass to transparent soda-lime glass and shock waves formation
  
  • Sow Mohamed Chérif
  • Blondeau Jean-Philippe
  • Sagot Nadine
  • Ollier Nadège
  • Tite Teddy
  Applied Surface Science, Elsevier, 2015, 336, pp.255-261. In this contribution, we showed for the first time in our knowledge a single-step process for silver clusters and nanoparticles growth and transfer from silver-exchanged soda-lime glass to un-exchanged soda-lime glass (transparent glass in visible and NIR domain) by nanosecond (ns) laser irradiation. The transferred silver nanoparticles in transparent glass are strongly linked to the glass surface. In addition, we point out the formation of shock waves, with selective silver clustering on the top wave. This technique provides an alternative and simple way to obtain metallic nanoparticles in different media which can be traversed by laser wavelength used. Moreover, this experiment is made at room temperature and air environment. It is worth noting that our technique requires a glass previously doped with the corresponding silver ions. (10.1016/j.apsusc.2014.11.158)
  DOI : 10.1016/j.apsusc.2014.11.158
• Spin-transfer torque effects in the dynamic forced response of the magnetization of nanoscale ferromagnets in superimposed ac and dc bias fields in the presence of thermal agitation
  
  • Byrne D. J.
  • Coffey W. T.
  • Kalmykov Y. P.
  • Titov S. V.
  • Wegrowe J. E.
  Biophysical Reviews and Letters, World Scientific Publishing, 2015, 91 (17). (10.1103/PhysRevB.91.174406)
  DOI : 10.1103/PhysRevB.91.174406
• Conception in silico d'une nouvelle phase de carbure de bore
  
  • Jay Antoine
  , 2015. Le but de ce travail est de renforcer le carbure de bore à 20% d’atomes de carbone B 4 C pour son utilisation pour le blindage. Cette thèse a été consacrée à l’étude théorique d’une nouvelle phase de carbure de bore à l’aide des méthodes ab initio basées sur la théorie de la fonctionnelle de la densité (DFT), en utilisant l’approximation de la densité locale (LDA) et du gradient généralisé (GGA). Les méthodes employées ont tout d’abord été validées en comparant les résultats calculés aux résultats expérimentaux sur le carbure de bore B 4 C. Elles ont ensuite été utilisées pour concevoir de nouveaux matériaux. L’idée a été de renforcer les chaînes C-B-C par rapport à la formation de lacunes. Dans le nouveau matériau, (B 11 C p )C-C, les chaînes sont C-C. En me basant sur le modèle io- nique de Wade, j’ai aussi trouvé qu’augmenter la concentration en carbone sur l’icosaèdre, (B 10 C 2 )C-C, forme une deuxième phase métastable. La concentration obtenue (28% en atomes de carbone) sort toutefois du domaine connu d’existence des phases icosaédriques. Une fois les structures conçues, la deuxième étape a été de vérifier leur (méta)stabilité. Cela a nécessité le calcul de leurs énergies de formation, de leurs constantes élastiques et des courbes de dispersion des phonons. La troisième étape a été de vérifier le renforcement mécanique. Pour cela, j’ai démontré que ces matériaux sont moins sujets à la formation de lacunes, et que les lacunes qui peuvent se former ne subissent pas de réduction dis- continue de volume sous pression hydrostatique contrairement à ce qu’il se passe pour B 4 C. De plus, les propriétés élastiques calculées ont montré une augmentation du module d’incompressibilité, du module de Young et du module de cisaillement. J’ai montré que différentes méthodes peuvent permettre de différencier les matériaux à chaînes C-C, et plus particulièrement (B 11 C p )C-C, de B 4 C. Ces méthodes sont la diffrac- tion des rayons X et la spectroscopie vibrationnelle Raman et infrarouge. En particulier, j’ai identifié tous les modes propres de (B 11 C p )C-C en projetant leurs vecteurs propres sur ceux de B 4 C et j’ai calculé leur spectre de diffusion Raman en moyenne polycris- talline. J’ai aussi étudié le spectre Raman de B 4 C sous pression et les résultats sont en excellent accord avec l’expérience. Cela m’a permis de valider les identifications des modes réalisées à pression ambiante et de comprendre la différence entre le calcul en symétrie monoclinique et l’expérience en moyenne rhomboédrique. Dans le but de proposer une méthode de synthèse, j’ai ensuite étudié la transition de phase pouvant se produire sous pression entre le matériau (B 11 C p )CC ( représente une lacune) et le matériau (B 11 C p )C-C. Une méthode de synthèse a été élaborée dans le but de réaliser ce matériau. Cette méthode est une magnésiothermie sous haute pression.
• Estimating Excitonic Effects in the Absorption Spectra of Solids: Problems and Insight from a Guided Iteration Scheme
  
  • Rigamonti Santiago
  • Botti Silvana
  • Véniard Valérie
  • Draxl Claudia
  • Reining Lucia
  • Sottile Francesco
  Physical Review Letters, American Physical Society, 2015, 114 (14). A major obstacle for computing optical spectra of solids is the lack of reliable approximations for capturing excitonic effects within time-dependent density functional theory. We show that the accurate prediction of strongly bound electron-hole pairs within this framework using simple approximations is still a challenge and that available promising results have to be revisited. Deriving a set of analytical formulas we analyze and explain the difficulties. We deduce an alternative approximation from an iterative scheme guided by previously available knowledge, significantly improving the description of exciton binding energies. Finally, we show how one can “read” exciton binding energies from spectra determined in the random phase approximation, without any further calculation. (10.1103/PhysRevLett.114.146402)
  DOI : 10.1103/PhysRevLett.114.146402
• Limitations to laser machining of silicon using femtosecond micro-Bessel beams in the infrared
  
  • Grojo David
  • Mouskeftaras Alexandros
  • Delaporte Philippe
  • Lei Shuting
  Journal of Applied Physics, American Institute of Physics, 2015, 117 (15). We produce and characterize high-angle femtosecond Bessel beams at 1300-nm wavelength leading to nonlinearly ionized plasma micro-channels in both glass and silicon. With microjoule pulse energy, we demonstrate controlled through-modifications in 150-mu m glass substrates. In silicon, strong two-photon absorption leads to larger damages at the front surface but also a clamping of the intensity inside the bulk at a level of approximate to 4 x 10(11) W cm(-2) which is below the threshold for volume and rear surface modification. We show that the intensity clamping is associated with a strong degradation of the Bessel-like profile. The observations highlight that the inherent limitation to ultrafast energy deposition inside semiconductors with Gaussian focusing [Mouskeftaras et al., Appl. Phys. Lett. 105, 191103 (2014)] applies also for high-angle Bessel beams. (C) 2015 AIP Publishing LLC. (10.1063/1.4918669)
  DOI : 10.1063/1.4918669
• Effects of low-energy excitations on spectral properties at higher binding energy: The metal-insulator transition of VO$_2$
  
  • Gatti Matteo
  • Panaccione Giancarlo
  • Reining Lucia
  Physical Review Letters, American Physical Society, 2015, 114 (11), pp.116402. The effects of electron interaction on spectral properties can be understood in terms of coupling between excitations. In transition metal oxides the spectral function close to the Fermi level and low-energy excitations between d states have attracted particular attention. In this work we focus on photoemission spectra of vanadium dioxide over a wide (10 eV) range of binding energies. We show that there are clear signatures of the metal-insulator transition over the whole range due to a cross coupling of the delocalized s and p states with low-energy excitations between the localized d states. This coupling can be understood by advanced calculations based on many-body perturbation theory in the GW approximation. We also advocate the fact that tuning the photon energy up to the hard X-ray range can help to distinguish fingerprints of correlation from pure bandstructure effects. (10.1103/PhysRevLett.114.116402)
  DOI : 10.1103/PhysRevLett.114.116402
• Spin-transfer torque effects in the dynamic forced response of the magnetization of nanoscale ferromagnets in superimposed ac and dc bias fields in the presence of thermal agitation
  
  • Coffey William T.
  • Kalmykov Yuri P.
  • Titov Serguey V.
  • Byrne Declan J.
  • Wegrowe Jean-Eric
  , 2015.
• Ultrafast dynamics of fluctuations in high-temperature superconductors far from equilibrium
  
  • Perfetti L.
  • Sciolla B.
  • Biroli G.
  • van Der Beek C. J.
  • Piovera C.
  • Wolf M.
  • Kampfrath T.
  Physical Review Letters, American Physical Society, 2015, 114 (6), pp.067003. Despite extensive work on high-temperature superconductors, the critical behavior of an incipient condensate has so far been studied exclusively under equilibrium conditions. Here, we excite Bi2Sr2CaCu2O8+d with a femtosecond laser pulse and monitor the subsequent nonequilibrium dynamics of the mid-infrared conductivity. Our data allow us to discriminate temperature regimes where superconductivity is either coherent, fluctuating or vanishingly small. Above the transition temperature Tc, we make the striking observation that the relaxation to equilibrium exhibits power-law dynamics and scaling behavior, both for optimally and underdoped superconductors. Our findings can in part be modeled using time-dependent Ginzburg-Landau theory and provide strong indication of universality in systems far from equilibrium. (10.1103/PhysRevLett.114.067003)
  DOI : 10.1103/PhysRevLett.114.067003
• Impact of rare earth element clusters on the excited state lifetime evolution under irradiation in oxide glasses
  
  • Pukhkaya Vera
  • Goldner Philippe
  • Ferrier Alban
  • Ollier Nadège
  Optics Express, Optical Society of America - OSA Publishing, 2015, 23 (3), pp.3270-3281. Rare earth doped active glasses and fibers can be exposed to ionizing radiations in space and nuclear applications. In this work, we analyze the evolution of 2 F 5/2 excited state lifetime in Yb 3+ ions in irradiated aluminosilicate glasses by electrons and γ rays. It is found that the variation of lifetimes depends on the Yb 3+ clusters content of the glasses for irradiation doses in the 10 2 – 1.5·10 9 Gy range. In particular, glasses with high clustering show a smaller decrease in lifetime with increasing radiation dose. This behavior is well correlated to the variation in paramagnetic defects concentration determined by electron paramagnetic resonance. This effect is also observed in Yb 3+ doped phosphate and Er 3+ doped aluminosilicate glasses, inferring that clustering plays an important role in irradiation induced quenching. (10.1364/OE.23.003270)
  DOI : 10.1364/OE.23.003270
• MOVPE growth of InGaN alloys with high In content on ZnO template substrates
  
  • Sundaram Suresh
  • Puybaret Renaud
  • Rogers Dave J.
  • Teherani Ferechteh Hosseini
  • Sandana Eric Vinod
  • Bove Philippe
  • El Gmili Youssef
  • Troadec David
  • Patriarche Gilles
  • Voss Paul L
  • Salvestrini Jean-Paul
  • Ougazzaden Abdallah
  , 2015.
• Quelques applications industrielles de la chimie des radiations
  
  • Clochard Marie-Claude
  • L Wade Travis
  • Wegrowe Jean-Eric
  La jaune et la rouge [revue mensuelle de la société amicale des anciens élèves de l'Ecole Polytechnique], Association des anciens élèves de l'Ecole Polytechnique, 2015 (702), pp.18-19.
• Quasiparticle excitations in the photoemission spectrum of CuO from first principles: A GW study
  
  • Rödl Claudia
  • Sottile Francesco
  • Reining Lucia
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2015, 91, pp.045102. We present ab initio quasiparticle calculations for electronic excitations and the fundamental band gap of the strongly correlated transition-metal oxide CuO using the GW approximation of many-body perturbation theory. Problems related to the suitability of the method for strongly correlated materials and issues of self-consistency are addressed. We explain why quasiparticle self-consistent GW strongly overestimates the band gap of CuO. Apart from the band gap, electron addition and removal spectra in the quasiparticle approximation including lifetime and matrix-element effects are found to be in excellent agreement with the quasiparticle excitations in direct and inverse photoemission data. (10.1103/PhysRevB.91.045102)
  DOI : 10.1103/PhysRevB.91.045102
• Matériaux luminescents pour des applications optoélectroniques
  
  • Marghad Ikbal
  • Cosmini C.
  • Beek K. van Der
  • Zissis Georges
  , 2015.
• Orientation effect on the giant stress field induced in a single Ni nanowire by mechanical strain
  
  • Melilli G.
  • Madon B.
  • Clochard M.-C.
  • Wegrowe J.-E.
  , 2015, pp.95512Y. The change of magnetization (i.e. using the inverse magnetostriction effect) allows to investigate at the nanoscale the effects of thermoelastic and piezoelectric strain of an active track-etched β-PVDF polymer matrix on an electrodeposited single-contacted Ni nanowire (NW). The magnetization state is measured locally by anisotropic magnetoresitance (AMR). The ferromagnetic NW plays thus the role of a mechanical probe that allows the effects of mechanical strain to be characterized and described qualitatively and quantitatively. Due to the inverse magnetostriction, a quasi-disappearance of the AMR signal for a variation of the order of ΔT ≈ 10 K has been evidenced. The coplanarity of the vectors between the magnetization and the magnetic field is broken. A way of studying the effect of the geometry on such a system, is to fabricate oriented polymer templates. Track-etched polymer membranes were thus irradiated at various angles (αirrad) leading, after electrodeposition, to embedded Ni NWs of different orientations. With cylindrical Ni NW oriented normally to the template surface, the induced stress field in a single Ni NW was found 1000 time higher than the bulk stress field (due to thermal expansion measured on the PVDF). This amplification results in three nanoscopic effects: (1) a stress mismatch between the Ni NW and the membrane, (2) a non-negligible role of the surface tension on Ni NW Young modulus, and (3) the possibility of non-linear stress-strain law. When the Ni NWs are tilted from the polymer template surface normality, the induced stress field is reduced and the amplification phenomenon is less important. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. (10.1117/12.2189085)
  DOI : 10.1117/12.2189085
• Anomalous excitons and screenings unveiling strong electronic correlations in SrTi1−xNbxO3 (0≤x≤0.005)
  
  • Gogoi Pranjal Kumar
  • Sponza Lorenzo
  • Schmidt Daniel
  • Asmara Teguh Citra
  • Diao Caozheng
  • Lim Jason C. W.
  • Poh Sock Mui
  • Kimura Shin-Ichi
  • Trevisanutto Paolo E.
  • Olevano Valerio
  • Rusydi Andrivo
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2015, 92 (3), pp.035119. Electron-electron (e-e) and electron-hole (e-h) interactions are often associated with many exotic phenomena in correlated electron systems. Here, we report an observation of anomalous excitons at 3.75 , 4.67 and 6.11 eV at 4.2 K in $bulk$-SrTiO$_3$. Fully supported by $ab\ initio$ GW Bethe-Salpeter equation calculations, these excitons are due to surprisingly strong e-h and e-e interactions with different characters: 4.67 and 6.11 eV are resonant excitons and 3.75 eV is a bound Wannier-like exciton with an unexpectedly higher level of delocalization. Measurements and calculations on SrTi$_{1-x}$Nb$_x$O$_3$ for 0.0001$\leq$x$\leq$0.005 further show that energy and spectral-weight of the excitonic peaks vary as a function of electron doping (x) and temperature, which are attributed to screening effects. Our results show the importance of e-h and e-e interactions yielding to anomalous excitons and thus bring out a new fundamental perspective in SrTiO$_3$. (10.1103/PhysRevB.92.035119)
  DOI : 10.1103/PhysRevB.92.035119
• Silica nanoparticle core structure examined by the E?Si? center 29Si strong hyperfine interaction
  
  • Alessi A.
  • Agnello S.
  • Buscarino G.
  • Boizot B.
  • Cannas M.
  • Gelardi F.M.
  Journal of Non-Crystalline Solids, Elsevier, 2015, 423-424, pp.41 - 44. (10.1016/j.jnoncrysol.2015.05.022)
  DOI : 10.1016/j.jnoncrysol.2015.05.022
• Simple scalings for various regimes of electron acceleration in surface plasma waves
  
  • Riconda C.
  • Raynaud M.
  • Vialis T.
  • Grech M.
  Physics of Plasmas, American Institute of Physics, 2015, 22 (7), pp.073103. Different electron acceleration regimes in the evanescent field of a surface plasma wave are studied by considering the interaction of a test electron with the high-frequency electromagnetic field of a surface wave. The non-relativistic and relativistic limits are investigated. Simple scalings are found demonstrating the possibility to achieve an efficient conversion of the surface wave field energy into electron kinetic energy. This mechanism of electron acceleration can provide a high-frequency pulsed source of relativistic electrons with a well defined energy. In the relativistic limit, the most energetic electrons are obtained in the so-called electromagnetic regime for surface waves. In this regime, the particles are accelerated to velocities larger than the wave phase velocity, mainly in the direction parallel to the plasma-vacuum interface. (10.1063/1.4923443)
  DOI : 10.1063/1.4923443
• Transfer of spectral weight across the gap of Sr₂IrO₄ induced by La doping
  
  • Brouet Véronique
  • Mansart Joseph
  • Perfetti Luca
  • Piovera Christian
  • Vobornik Ivana
  • Le Fèvre Patrick
  • Bertran François
  • Riggs Scott
  • Shapiro M.
  • Giraldo-Gallo Paula
  • Fisher Ian
  Physical Review B, American Physical Society, 2015, 92 (8), pp.081117. We study with Angle Resolved PhotoElectron Spectroscopy (ARPES) the evolution of the electronic structure of Sr₂IrO₄, when holes or electrons are introduced, through Rh or La substitutions. At low dopings, the added carriers occupy the first available states, at bottom or top of the gap, revealing an anisotropic gap of 0.7eV in good agreement with STM measurements. At further doping, we observe a reduction of the gap and a transfer of spectral weight across the gap, although the quasiparticle weight remains very small. We discuss the origin of the in-gap spectral weight as a local distribution of gap values. (10.1103/PhysRevB.92.081117)
  DOI : 10.1103/PhysRevB.92.081117
• What time-resolved measurements tell us about femtosecond laser damage?
  
  • Melnikaitis Andrius
  • Siaulys Nerijus
  • Momgaudis Balys
  • Vaicenavičius Julius
  • Barkauskaitė Simona
  • Sirutkaitis Valdas
  • Gallais Laurent
  • Guizard Stéphane
  , 2015, 9632, pp.96320O.
• Poly(4-vinyl pyridine) radiografted PVDF track etched membranes as sensors for monitoring trace mercury in water
  
  • Bessbousse H
  • Zran N
  • Fauléau J
  • Godin B
  • Lemée V
  • Wade T
  • Clochard Marie-Claude
  International Journal for Radiation Physics and Chemistry, Elsevier, 2015, pp.in press. Poly-4-vinyl pyridine chains were radiografted inside the etched-tracks of PVDF nanoporous membrane. P4VP grafting was found to be localized on the solid PVDF surface. Coating of these PVDF-g-P4VP membranes with a very thin layer of gold results in an ASV electrochemical sensor. Functionalized ion track-etched PVDF-g-P4VP sensors were found very selective and highly sensitive for mercury LOD 5 ng/L. a b s t r a c t By a radiation-induced grafting technique, we have functionalized track-etched nanoporous polymer membranes with mercury sensitive poly-4-vinyl pyridine (P4VP). Coating of these membranes with a very thin layer of gold results in an electrochemical sensor that is very selective and highly sensitive for mercury LOD 5 ng/L – well below the norms for water (0.015 mg/L potable water and 0.5 mg/L residual waters-French water norms of 27 October 2011). E-beam irradiation permitted optimization of the radiografting synthesis on PVDF thin films prior to ion-track grafting. Synthesis and characterization by EPR, FESEM and FTIR are described in detail. A comparison between FTIR in ATR and transmission modes enabled us to localize the grafting on the surface of the e-beam irradiated PVDF films allowing us to extrapolate what happens on the etched tracks. Using Square Wave Anodic Stripping Voltammetry (SW-ASV), mercury concentrations of 1 mg/L are detected in 2 h and low ng/L concentrations are detected after 24 h of adsorption. The adsorption is passive so sensors do not require instrumentation and the analysis takes only 3–4 min. Also, the P4VP functionalized sensor appears insensitive to pH variations (pHs 3–9), high salt concentrations (up to 1 g/ L) and the presence of other heavy metals in the same solution. & (10.1016/j.radphyschem.2015.03.011)
  DOI : 10.1016/j.radphyschem.2015.03.011
• Delayed fluorescence on triazine carbazole derivative
  
  • Marghad Ikbal
  • Clochard M. C.
  • Ollier N.
  • Wade Travis L.
  • Aymes-Chodur C.
  • Renaud Cédric
  • Zissis Georges
  , 2015.
• Quasiparticle dynamics in high-temperature superconductors far from equilibrium: An indication of pairing amplitude without phase coherence
  
  • Piovera C.
  • Zhang Zhongkai
  • d'Astuto M.
  • Taleb-Ibrahimi A.
  • Papalazarou E.
  • Marsi M.
  • Li Z.
  • Raffy H.
  • Perfetti L.
  Physical Review B, American Physical Society, 2015, 91 (22), pp.224509. We perform time-resolved photoelectron spectroscopy measurements of optimally doped $Bi_2Sr_2CaCu_2O_{8+δ}$ (Bi-2212) and $Bi_2Sr_{2−x}La_xCuO_{6+δ}$ (Bi-2201). The electron dynamics shows that inelastic scattering by nodal quasiparticles decreases when the temperature is lowered below the critical value of the superconducting phase transition. This drop in electronic dissipation is astonishingly robust and survives to photoexcitation densities much larger than the value sustained by long-range superconductivity. The unconventional behavior of quasiparticle scattering is ascribed to superconducting correlations extending on a length scale comparable to the inelastic path. Our measurements indicate that strongly driven superconductors enter in a regime without phase coherence but finite pairing amplitude. The latter vanishes near to the critical temperature and has no evident link to the pseudogap observed by angle-resolved photoelectron spectroscopy. (10.1103/PhysRevB.91.224509)
  DOI : 10.1103/PhysRevB.91.224509
• Thermally activated delayed fluorescence evidence in non-bonding transition electron donor-acceptor molecules
  
  • Marghad Ikbal
  • Clochard M.
  • Ollier N.
  • Wade Travis
  • Aymes-Chodur C.
  • Renaud Cédric
  • Zissis Georges
  , 2015, pp.956629. The exhibition of thermally activated delayed fluorescence on triazine derivative by the introduction of a nonbonding part is demonstrated. Two molecules containing triazine core as acceptor and carbazole part as donor has been synthesized and characterized. One of these molecules bears an additional nonbonding part by the means of a phenoxy group. The results indicated that the molecule bearing the nonbonding molecular part (phenoxy) exhibit thermally activated delayed fluorescence while not on molecule free of non-bonding group. The results are supported by, photoluminescence, spectral analysis time-resolved fluorescence and time-dependent density functional estimation. (10.1117/12.2186802)
  DOI : 10.1117/12.2186802