76 research outputs found
Structural dynamics in atomic indium wires on silicon: From ultrafast probing to coherent vibrational control
No full texthttp://dx.doi.org/10.13039/501100003006 ETH Zürichhttp://dx.doi.org/10.13039/100010663 ERChttp://dx.doi.org/10.13039/501100000781 European Research Councilhttp://dx.doi.org/10.13039/501100001659 DF
Nawoord: Over veldwerk en antropologie als wetenschap
No full textSince the 1970s anthropologists write in a more reflexive way about their fieldwork. Anthropologist and travel author Gerrit Jan Zwier wrote a book about the rise of this genre. He asked the historian and anthropologist Yme Kuiper to add an epilogue to a new edition of his classic (first published in 1980)
Mode-selective ballistic pathway to a metastable electronic phase
Full text linkExploiting vibrational excitation for the dynamic control of material properties is an attractive goal with wide-ranging technological potential. Most metal-to-insulator transitions are mediated by few structural modes and are, thus, ideal candidates for selective driving toward a desired electronic phase. Such targeted navigation within a generally multi-dimensional potential energy landscape requires microscopic insight into the non-equilibrium pathway. However, the exact role of coherent inertial motion across the transition state has remained elusive. Here, we demonstrate mode-selective control over the metal-to-insulator phase transition of atomic indium wires on the Si(111) surface, monitored by ultrafast low-energy electron diffraction. We use tailored pulse sequences to individually enhance or suppress key phonon modes and thereby steer the collective atomic motion within the potential energy surface underlying the structural transformation. Ab initio molecular dynamics simulations demonstrate the ballistic character of the structural transition along the deformation vectors of the Peierls amplitude modes. Our work illustrates that coherent excitation of collective modes via exciton-phonon interactions evades entropic barriers and enables the dynamic control of materials functionality
Non-thermal phonon dynamics and a quenched exciton condensate probed by surface-sensitive electron diffraction
No full textISSN:1476-1122ISSN:1476-4660ISSN:1476-466
Structural phase transitions and phase ordering at surfaces probed by ultrafast LEED
No full textWe demonstrate the capability of ultrafast low-energy electron diffraction to resolve phase-ordering kinetics and structural phase transitions on their intrinsic time scales with ultimate surface sensitivity
Ander Theil der Schifffahrten Joann Huygens von Lintschotten ..., so er in Orient gethan, begriffen, und fürnemlich alle Gelegenheit derselbigen Landen, Insulen, Meerpforten &c., so unter wegen auffstossen und dann in India fürkommen, wie auch alles, was der Author allda ... gesehen und erfahren, eygentlich beschrieben wirdt
No full textAlles ... von neuwem auss den Niderländischen Exemplarien in Hochteutsch bracht und ... zusammen gefügt, sampt vielen ... Figurn und Landtafeln, in Kupffer gestochen, und an Tag geben durch Io. Theodor und Io. Israel de Bry .... II. Der Holländer Schifffahrt in die Orientalische Insulen, Iauan vnd Sumatra, sampt Sitten, Leben und Superstition &c. der Völcker. III. Drey Schifffahrten der Holländer nach obermeldten Indien durch das Mittnächtigsche oder Eissmeer ...Der zweite Text ist von Willem Lodewycksz, der dritte von Gerrit de VeerBogensignaturen: )(⁶, A-Z, Aa-Ee⁴, Ff⁶, a-q⁴Originaltitel: Itinerario, voyage ofte schipvaert, van Jan Huygen van Linschoten naer Oost ofte Portugaels IndienOriginaltitel: D'eerste boeck, Historie van Indien, waer inne verhaelt is de avontueren die de Hollandtsche schepen bejeghent zijn / [Willem Lodewycksz]Originaltitel: Waerachtighe beschryvinghe van drie seylagien / Gerrit de VeerAus Vorbesitz der Naturforschenden Gesellschaft in Zürich
Surface structure and stacking of the commensurate charge density wave phase of
Full text linkBy quantitative low-energy electron diffraction (LEED) we investigate the extensively studied commensurate charge density wave (CDW) phase of trigonal tantalum disulphide (1T−TaS2), which develops at low temperatures with a (13×13)R13.9∘ periodicity. A full-dynamical analysis of the energy dependence of diffraction spot intensities reveals the entire crystallographic surface structure, i.e., the detailed atomic positions within the outermost two trilayers consisting of 78 atoms as well as the CDW stacking. The analysis is based on an unusually large data set consisting of spectra for 128 inequivalent beams taken in the energy range 20–250 eV and an excellent fit quality expressed by a best-fit Pendry R factor of R=0.110. The LEED intensity analysis reveals that the well-accepted model of star-of-David-shaped clusters of Ta atoms for the bulk structure also holds for the outermost two TaS2 trilayers. Specifically, in both layers the clusters of Ta atoms contract laterally by up to 0.25 Å and also slightly rotate within the superstructure cell, causing respective distortions as well as heavy bucklings (up to 0.23 Å) in the adjacent sulfur layers. Most importantly, our analysis finds that the CDWs of the first and second trilayers are vertically aligned, while there is a lateral shift of two units of the basic hexagonal lattice (6.71 Å) between the second and third trilayers. The results may contribute to a better understanding of the intricate electronic structure of the reference compound 1T−TaS2 and guide the way to the analysis of complex structures in similar quantum materials
Valley-controlled photoswitching of metal-insulator nanotextures
Full text linkSpatial heterogeneity and phase competition are hallmarks of strongly correlated materials, influencing phenomena such as colossal magnetoresistance and high-temperature superconductivity. Active control over phase textures further promises tunable functionality at the nanoscale. Although light-induced switching of a correlated insulator to a metallic state is well established, optical excitation generally lacks the specificity to select subwavelength domains and determine final textures. Here we drive the domain-specific quench of a textured Peierls insulator using valley-selective photodoping. Polarized excitation exploits the anisotropy of quasi-one-dimensional states at the charge-density-wave gap to initiate an insulator–metal transition with minimal electronic heating. We find that averting dissipation facilitates domain-specific carrier confinement, control over nanotextured phases and reduction in thermal relaxation from the metastable metallic state. This valley-selective photoexcitation approach will enable the activation of electronic phase separation beyond thermodynamic limitations, facilitating optically controlled hidden states, engineered heterostructures and polarization-sensitive percolation networks
Nawoord: Over veldwerk en antropologie als wetenschap
No full textVooral in de openhartige jaren zestig en zeventig van de vorige eeuw bloeide het genre van de 'antropologische bekentenisliteratuur' op. Met een zekere gretigheid brachten antropologen verslag uit van de spanningen en frustraties waaronder zij in het 'veld' gebukt waren gegaan. Ineens was de tijd voorbij dat zij in het voorwoord van een gedegen etnografie hun cultuurschok slechtsin enkele achteloze zinnen afdeden. Al deze openbare biechten maakten de lezer duidelijk dat het pad van een veldwerker bezaaid was met distels en doornen, al bevond zich daartussen gelukkigook wel eens een enkel madeliefje. In Antropologen te velde klinken de stemmen op van bekende en minder bekende antropologen. Te samen geven zij een kleurrijk, indringend en vaak humoristisch beeld van het leven en lijden van de veldwerker. Het boek geeft een uitstekende kijk in de keuken van de klassieke antropologie en laat vele grootheden uit de vroege veldwerktraditie aan het woord.Since the 1970s anthropologists write in a more reflexive way about their fieldwork.Anthropologist and travel author Gerrit Jan Zwier wrote a book about the rise of this genre. He asked the historian and anthropologist Yme Kuiper to add an epilogue to a new edition of his classic (first published in 1980)
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