Transition énergétique

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.

We report on magnetization M(H), dc and ac magnetic susceptibility Χ(T), specific heat C_m(T) and muon spin relaxation (μSR) measurements of the Kitaev honeycomb iridate Cu₂IrO₃ with quenched disorder. In spite of the chemical disorders, we find no indication of spin glass down to 260 mK from the C_m(T) and μSR data.

Plenary Session Featuring The Fred Kavli Distinguished Lectureship in Materials Science:

Tuesday, April 23

8:15 am – 9:30 am

PCC North, 100 Level, Ballroom 120 D

SIM beamline scientist Carlos Vaz was recognized as outstanding referee for providing high quality peer review for the Journal of Materials Chemistry C (Royal Society of Chemistry).

Lithography‐like writing of conducting regions at the interface between SrTiO₃ and amorphous Si using X‐ray irradiation opens ways for spatially controlled functionalities in oxide heterostructures.

Water is a ubiquitous liquid with unique physicochemical properties, whose nature has shaped our planet and life as we know it. Water in restricted geometries has different properties than in bulk. Confinement can prevent low-temperature crystalliza- tion of the molecules into a hexagonal structure and thus create a state of amorphous water. To understand the survival of life at subzero temperatures, it is essential to elucidate this behaviour in the presence of nanoconfining lipidic membranes.