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Université de Fribourg

Time- and angle-resolved photoemission spectroscopy of solids in the extreme ultraviolet at 500 kHz repetition rate

Puppin, M. ; Deng, Y. ; Nicholson, C. W. ; Feldl, J. ; Schröter, N. B. M. ; Vita, H. ; Kirchmann, P. S. ; Monney, Claude ; Rettig, L. ; Wolf, M. ; Ernstorfer, R.

In: Review of Scientific Instruments, 2019, vol. 90, no. 2, p. 023104

Time- and angle-resolved photoemission spectroscopy (trARPES) employing a 500 kHz extreme-ultraviolet light source operating at 21.7 eV probe photon energy is reported. Based on a high-power ytterbium laser, optical parametric chirped pulse amplification, and ultraviolet-driven high-harmonic generation, the light source produces an isolated high-harmonic with 110 meV bandwidth and a flux of...

Université de Fribourg

Spin-freezing and the Sachdev-Ye model

Werner, Philipp ; Kim, Aaram J. ; Hoshino, Shintaro

In: EPL (Europhysics Letters), 2018, vol. 124, no. 5, p. 57002

Spin-freezing is the origin of bad-metal physics and non-Fermi liquid (non-FL) properties in a broad range of correlated compounds. In a multi-orbital lattice system with Hund coupling, doping of the half-filled Mott insulator results in a highly incoherent metal with frozen magnetic moments. These moments fluctuate and collapse in a crossover region that is characterized by unusual non-Fermi...

Université de Fribourg

Beyond the molecular movie: Dynamics of bands and bonds during a photoinduced phase transition

Nicholson, Christopher W. ; Lücke, A. ; Schmidt, W. G. ; Puppin, M. ; Rettig, L. ; Ernstorfer, R. ; Wolf, M.

In: Science, 2018, vol. 362, no. 6416, p. 821–825

Ultrafast nonequilibrium dynamics offer a route to study the microscopic interactions that govern macroscopic behavior. In particular, photoinduced phase transitions (PIPTs) in solids provide a test case for how forces, and the resulting atomic motion along a reaction coordinate, originate from a nonequilibrium population of excited electronic states. Using femtosecond photoemission, we...

Université de Fribourg

Temperature-driven topological phase transition and intermediate Dirac semimetal phase in ${\mathrm{ZrTe}}_{5}$

Xu, B. ; Zhao, L. X. ; Maršík, Premysl ; Sheveleva, E. ; Lyzwa, F. ; Dai, Y. M. ; Chen, G. F. ; Qiu, X. G. ; Bernhard, Christian

In: Physical Review Letters, 2018, vol. 121, no. 18, p. 187401

We present an infrared spectroscopy study of ZrTe5, which confirms a recent theoretical proposal that this material exhibits a temperature-driven topological quantum phase transition from a weak to a strong topological insulating state with an intermediate Dirac semimetal state around Tp ≃ 138 K. Our study details the temperature evolution of the energy gap in the bulk electronic structure....

Université de Neuchâtel

Measurement of the linewidth enhancement factor of singlemode room temperature continuous wave quantum cascade lasers

Aellen, Thierry ; Aebi, Philipp (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2008.

L'invention des sources lasers en 1960 a conduit à un bon nombre d'applications qui ont un impact répandu dans tous les aspects de notre votre vie actuelle, citons notamment l'exemple des hôpitaux, de l'industrie ou simplement dans notre lieu de vie. Les derniers développements sont en particulier issus des compacts, très efficace et populaires lasers semiconducteurs qui sont simplement...

Haute école de gestion de Genève

Acceptance of digital payment methods in Switzerland

Milla Rodriguez, Allison ; Depetris Chauvin, Nicolas (Dir.)

Mémoire de bachelor : Haute école de gestion de Genève, 2018 ; TDIBM 41.

The advent of the technology brings new possibilities in term of payment solutions and as a consequence the use of cash is declining. There are even regulations that force people to pay by electronic methods depending on the amount/or the country. These regulations limit the amount of cash in a single transaction to combat illegal practices. Indeed, cashless payment methods offer transparency and...

Université de Fribourg

Linear behavior of the optical conductivity and incoherent charge transport in ${\mathrm{BaCoS}}_{2}$

Santos-Cottin, D. ; Klein, Y. ; Werner, Philipp ; Miyake, Takashi ; Medici, L. de ; Gauzzi, A. ; Lobo, R. P. S. M. ; Casula, Michele

In: Physical Review Materials, 2018, vol. 2, no. 10, p. 105001

Optical conductivity measurements on a BaCoS2 single crystal unveil an unusual linear behavior over a broad spectral range. In the paramagnetic phase above 300 K, the spectrum shows no gap, which contradicts the previously proposed scenario of a charge-transfer Mott insulator. Ab initio dynamical mean field theory calculations including a retarded Hubbard interaction explain the data in terms...

Université de Fribourg

Archaeometric analyses of european 18th–20th century white earthenware—a review

Maggetti, Marino

In: Minerals, 2018, vol. 8, no. 7, p. 269

This study provides an overview of the few archaeometric analyses of European white earthenwares from England, France, Italy, Slovenia, and Switzerland. White earthenwares were an extremely successful mass-product between ca. 1750 and 1900. They became “the porcelain of the poor man” and replaced the older traditional pottery such as faïence. The invention of this new ceramic type took...

Université de Fribourg

Integrated sensor system for DNA amplification and separation based on thin film technology

Costantini, Francesca ; Petrucci, Giulia ; Lovecchio, Nicola ; Nardecchia, Marco ; Nascetti, Augusto ; Cesare, Giampiero de ; Tedeschi, Lorena ; Domenici, Claudio ; Ruggi, Albert ; Placidi, Pisana ; Scorzoni, Andrea ; Caputo, Domenico

In: IEEE Transactions on Components, Packaging and Manufacturing Technology, 2018, vol. 8, no. 7, p. 1141–1148

This paper presents the development of a lab-on-chip, based on thin-film sensors, suitable for DNA treatments. In particular, the system performs on-chip DNA amplification and separation of double-strand DNA into single-strand DNA, combining a polydimethylsiloxane microfluidic network, thin-film electronic devices, and surface chemistry. Both the analytical procedures rely on the integration...

Université de Fribourg

Energy band-gap engineering of conjugated microporous polymers via acidity-dependent in situ cyclization

Lee, Jiyoung ; Buyukcakir, Onur ; Kwon, Tae-woo ; Coskun, Ali

In: Journal of the American Chemical Society, 2018, vol. 140, no. 35, p. 10937–10940

Conjugated microporous polymers (CMPs) offer a unique structure integrating π- conjugated backbone into a porous network for the simultaneous transport of charges and materials. However, tuning electronic properties of CMPs so far has been limited to an approach of varying the monomers, and the precious metal catalysts are inevitably needed for the C–C coupling reaction. Here, we present a...