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Ursula Keller wins “Swiss Nobel” Marcel Benoist Prize- for pioneering work in ultrafast lasers

Farewell: the NCCR MUST ended - on June 30, 2022

MUST2022 Conference- a great success!

New scientific highlights- by MUST PIs Wörner, Chergui, and Richardson

FELs of Europe prize for Jeremy Rouxel- “Development or innovative use of advanced instrumentation in the field of FELs”

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New FAST-Fellow Uwe Thumm at ETH- lectures on Topics in Femto- and Attosecond Science

International Day of Women and Girls in Science- SSPh asked female scientists about their experiences

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EU XFEL Young Scientist Award for Camila Bacellar,beamline scientist and group leader of the Alvra endstation at SwissFEL

Prizes for Giulia Mancini and Rebeca Gomez CastilloICO/IUPAP Young Scientist Prize in Optics & Ernst Haber 2021

Nobel Prize in Chemistry awarded to RESOLV Member Benjamin List- for the development of asymmetric organocatalysis

Hans Jakob Wörner invited to give the „New Horizons Solvay Lectures” - online, October 5, 12 and 19

Unusual keynote talk at an international scientific conference- Do photons show gender bias?

NCCR MUST at Scientifica 2021- Lightning, organic solar cells, and virtual molecules

Structural involvement in the melting of the charge density wave in 1T−TiSe2

March 1, 2021

It is commonly assumed that electronic phenomena occur at faster time scales than structural rearrangements. Here, we show the opposite: weak electronic excitations induce atomic displacements that outpace purely electronic charge carrier-interactions and hence are the dominant contribution in melting of the charge-density wave (CDW) in TiSe₂. This divergence of electronic and structural order is directly observed in experimental data from a transient ultrafast resonant/non-resonant X-Ray diffraction experiment. Our results create a paradigm shift that constitute a different, mechanistic pathway for phase transitions in the ultrafast regime.

Fig. 1. CDW phase and associated PLD upon cooling of $1 T - {TiSe}_{2}$ . (a) Simplified Fermi surface of a slice through Fermi pockets of holes (red, Se $4 p$ ) and electrons (blue, Ti $3 d$ ) in the first Brillouin zone at $\pm A$ along the $k_{c}$ axis, shown in the room-temperature (left) and CDW (right) phase. The band-folding of Ti $3 d$ and Se $4 p$ states accompanying the CDW transition is indicated, leading to a re-referencing of the Brillouin zone (e.g., the RT $L$ point becomes CDW $L / Γ^{*}$ point). (b) The 3D representation of the bands illustrates the $p - d$ splitting between the folded Se $4 p$ and Ti $3 d$ bands at $L / Γ^{*}$ , leading to excitonic correlations between electron-hole pairs (black dotted circle). (c) PLD associated with the CDW phase, causing a doubling of the unit cell along all three dimensions.

Reference: Burian, M., Porer, M., Mardegan, J.R.L., Esposito, V., Parchenko, S., Burganov, B., Gurung, N., Ramakrishnan, M., Scagnoli, V., Ueda, H., Francoual, S., Fabrizi, F., Tanaka, Y., Togashi, T., Kubota, Y., Yabashi, M., Rossnagel, K., Johnson, S.L., and Staub, U. (2021). Structural involvement in the melting of the charge density wave in 1T−TiSe2. Phys Rev Research 3, 013128. (10.1103/PhysRevResearch.3.013128)

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