Scientific Highlights
Moving Atoms by Photodoping
Understanding how and how fast we can drive atoms to create a structural phase transition is of fundamental interest as it directly relates to many processes in nature. Here we show that a photoexcitation can drive a purely structural phase transition before the energy is relaxed in the material that corresponds to a “warmer” equilibrated state.
Revealing a Living-Dead Magnetic Layer
A peculiar magnetic “dead layer” is detected at the surface of thin films of DyTiO3, a ferrimagnetic Mott insulator. Depth dependent X-ray absorption measurements performed at the X-Treme beamline in the Swiss Light Source indicate that this layer is associated with a deviation of the Ti valence from 3+ toward 4+ at the film surface, suppressing the magnetic coupling between Ti ions and unleashing a strong paramagnetic response from uncoupled Dy ions.
HERCULES at the Swiss Light Source
In the week of March 18-23 PSI welcomes 20 PhD students and postdocs taking part in the HERCULES 2018 school on Neutron and Synchrotron Radiation. They will attend lectures and perform two days of practical courses at several beam lines of the Swiss Light Source.
Photoinduced transitions in magnetoresistive manganites: A comprehensive view
Using the FEMTO slicing source at SLS, we have studied the structural response during the photoinduced transition in a charge-ordered Pr1-xCaxMnO3 thin films. By investigating the dynamics of both superlattice reflections and regular Bragg peaks, we disentangle the different structural contributions and analyze their relevant time-scales. Comparing these results with studies of the charge order and magnetic dynamics, a comprehensive picture of the phase transition linked to a single critical fluence fc is proposed.
Magnetic structures take a new turn
The unexpected finding that in an ‘artificial spin ice’ magnetostatic energy can be transformed into directed rotation of magnetization provides fresh insights into such nano-patterned magnetic structures — and might enable novel applications in nanoscale devices.
L'atmosphère à la lumière des rayons X
Des chercheurs du PSI ont développé une chambre d’expérience où ils reconstituent certains processus qui se jouent dans l’atmosphère et peuvent étudier ces derniers avec une précision inégalée grâce à de la lumière de type rayons X issue de la SLS. Lors de leurs premières expériences, ils ont étudié la formation du brome, qui joue un rôle essentiel dans la dégradation de l’ozone dans les couches inférieures de l’atmosphère. A l’avenir, cette nouvelle chambre d’expérience sera également mise à disposition de chercheurs d’autres disciplines scientifiques.
Single-shot Monitoring of Ultrafast Processes via X-ray Streaking at a Free Electron Laser
The advent of x-ray free electron lasers has extended the unique capabilities of resonant x-ray spectroscopy techniques to ultrafast time scales. Here, in collaboration between researchers from PSI, Sorbonne Universités, HASYLAB/DESY, Synchrotron SOLEIL, CNRS, and Uppsala University, we report on a novel experimental method that allows retrieving with a single x-ray pulse the time evolution of an ultrafast process, not only at a few discrete time delays, but continuously over an extended time window.
Moving atoms with enhanced
THz pulses and tracking them with ultrashort x-ray pulses on an XFEL
Controlled motions of atoms using ultrashort electric field pulses allow to manipulated the properties of a material on ultrafast timescales. Here we show how metallic structures can be used to enhance a THz electric field pulse and track the induced atomic motions with ultrashort x-ray pulses emitted by a X-ray free electron laser.
Nonlinear electron-phonon coupling in doped manganites
We employ time-resolved resonant x-ray diffraction to study the insulator-to-metal transition that is launched via resonant excitation of an infrared-active optical phonon mode in a half doped manganite. We find that the charge order reduces promptly with a highly nonlinear (quartic) dependence on excitation fluence.