Data Science

We have produced ultra-short X-ray FEL pulses at SwissFEL by strongly compressing low-charge electron beams.  Single-shot spectral measurements with only a single mode (see the figure below) indicate a pulse duration well below one femtosecond (detailed analysis on the exact pulse duration is ongoing).

A method to measure the superconducting (SC) stiffness tensor ρ_s, without subjecting the sample to external magnetic field, is applied to La_1.875Sr_0.125CuO₄. The method is based on the London equation J=-ρ_sA, where J is the current density and A is the vector potential which is applied in the SC state.

With a specific stimulus, shape‐memory materials can assume a temporary shape and subsequently recover their original shape, a functionality that renders them relevant for applications in fields such as biomedicine, aerospace, and wearable electronics. Shape‐memory in polymers and composites is usually achieved by exploiting a thermal transition to program a temporary shape and subsequently recover the original shape.

The properties of ligand protected gold nanoparticles are determined by the synergistic interplay of their structural components, including the metal core, the ligand shell, and the solvation layer. However, the simultaneous characterization of all these components remains a major challenge given their disparate chemical nature.

The Kondo effect, an eminent manifestation of many-body physics in condensed matter, is traditionally explained as exchange scattering of conduction electrons on a spinful impurity in a metal. The resulting screening of the impurity's local moment by the electron Fermi sea is characterized by a Kondo temperature T_K, below which the system enters a strongly coupled regime.

While information technology over the last 50 years has been based on conventional semiconductor electronics, future technologies – aiming to enhance the performance of computers, sensors and to secure data communication for the future internet – will use the quantum origins of nature.

This symposium highlighted the opportunities for the traditional semiconductor materials to remain the platform on which also the new quantum technologies will build on. The symposium, in part a celebration of the career of PSI Quantum Technologies group leader Hans Sigg, was held at ETHZ and included notable speakers both local and international, Gabriel Aeppli (PSI, ETHZ & EPFL), Jérôme Faist & Klaus Ensslin (ETHZ), Theo Rasing (RU Nijmegen), Giordano Scappucci (QuTech-TU Delft) and Klaus von Klitzing (MPI Stuttgart).

The progressive hydrostatic compression of I2 and I3- units in an organic salt lead to a homoatomic polymeric chain. As the I---I distance collapses the covalent character of the interaction becomes more relevant, leading to a pressure-tunable increased conductivity.

Elementary excitations in condensed matter capture the complex many-body dynamics of interacting basic entities in a simple quasiparticle picture. In magnetic systems the most established quasiparticles are magnons, collective excitations that reside in ordered spin structures, and spinons, their fractional counterparts that emerge in disordered, yet correlated spin states.

Researchers at NCCR MARVEL have combined first principles calculations with soft X-ray angle-resolved photoemission spectroscopy to examine tungsten diphosphide’s electronic structure, characterizing its Weyl nodes for the very first time. In agreement with density functional theory calculations, the results revealed two pairs of Weyl nodes lying at different binding energies. The observation of the Weyl nodes, as well as the tilted cone-like dispersions in the vicinity of the nodal points, provides compelling evidence that the material is a robust type-II Weyl semimetal with broken Lorentz invariance. This is as MARVEL researchers predicted two years ago. The research has been published in Physical Review Letters as an Editor's Suggestion.