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Publisher: Washington, DC : American Association for the Advancement of Science × WGL Institute: INM ×

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    Ultrafast dissolution and creation of bonds in IrTe2 induced by photodoping
    (Washington, DC : American Association for the Advancement of Science, 2018) Ideta, Shin-ichiro; Zhang, Dongfang; Dijkstra, Arend G; Artyukhin, Sergey; Keskin, Sercan; Cingolani, Roberto; Shimojima, Takahiro; Ishizaka, Kyoko; Ishii, Hiroyuki; Kudo, Kazutaka; Nohara, Minoru; Miller, R.J. Dwayne
    The observation and control of interweaving spin, charge, orbital, and structural degrees of freedom in materials on ultrafast time scales reveal exotic quantum phenomena and enable new active forms of nanotechnology. Bond- ing is the prime example of the relation between electronic and nuclear degrees of freedom. We report direct evidence illustrating that photoexcitation can be used for ultrafast control of the breaking and recovery of bonds in solids on unprecedented time scales, near the limit for nuclear motions. We describe experimental and theoretical studies of IrTe2 using femtosecond electron diffraction and density functional theory to investigate bonding instability. Ir-Ir dimerization shows an unexpected fast dissociation and recovery due to the filling of the antibonding dxy orbital. Bond length changes of 20% in IrTe2 are achieved by effectively addressing the bonds directly through this relaxation process. These results could pave the way to ultrafast switching between metastable structures by photoinduced manipulation of the relative degree of bonding in this manner.
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    Electron microscopy of nanoparticle superlattice formation at a solid-liquid interface in nonpolar liquids
    (Washington, DC : American Association for the Advancement of Science, 2020) Cepeda-Perez, E.; Doblas, D.; Kraus, T.; de Jonge, N.
    Nanoparticle superlattice films form at the solid-liquid interface and are important for mesoscale materials, but are notoriously difficult to analyze before they are fully dried. Here, the early stages of nanoparticle assembly were studied at solid-liquid interfaces using liquid-phase electron microscopy. Oleylamine-stabilized gold nanoparticles spontaneously formed thin layers on a silicon nitride (SiN) membrane window of the liquid enclosure. Dense packings of hexagonal symmetry were obtained for the first monolayer independent of the nonpolar solvent type. The second layer, however, exhibited geometries ranging from dense packing in a hexagonal honeycomb structure to quasi-crystalline particle arrangements depending on the dielectric constant of the liquid. The complex structures formed by the weaker interactions in the second particle layer were preserved, while the surface remained immersed in liquid. Fine-tuning the properties of the involved materials can thus be used to control the three-dimensional geometry of a superlattice including quasi-crystals.