PSI scientists have investigated a material that could be suitable for future data storage applications. They have manipulated the crystalline structure of their sample while measuring how this affects the material’s magnetic and electronic properties.
In topological materials, electrons can display behaviour that is fundamentally different from that in ‘conventional’ matter, and the magnitude of many such ‘exotic’ phenomena is directly proportional to an entity known as the Chern number. New experiments establish for the first time that the theoretically predicted maximum Chern number can be reached — and controlled — in a real material.
When magnetism meets topology, colorful novel states can emerge in condensed matter. It is widely believed that parity-time symmetry plays an essential role for the formation of Dirac states in Dirac semimetals. So far, all of the experimentally identified topological nontrivial Dirac semimetals possess both parity and time reversal symmetry. Since the magnetism will break time-reversal symmetry, only in special cases the Dirac states can be protected in a magnetic system. Thus, the realization of magnetic topological Dirac materials remains a major issue in the research of topological physics. In this work, the authors ascertained that the ground state of EuCd2As2 is a good candidate for magnetic topological Dirac semimetal when the spins point in the out-of-plane direction in the A-type antiferromagnetic phase. The Dirac state is protected by the combination of parity-time symmetry with additional translation operation. Moreover, when the spins deviate from out-of-plane direction, the bulk Dirac cone will open a gap, and the system develops into a novel state containing axion insulator, antiferromagnetic topological crystalline insulator, and higher order topological insulator.
A particular variety of particles, the so-called Weyl fermions, had previously only been detected in certain non-magnetic materials. But now researchers at PSI have experimentally proved their existence for the first time in a specific paramagnetic material.
Researchers at PSI have investigated a novel crystalline material at the Swiss Light Source SLS that exhibits electronic properties never seen before. Among other things, they were able to detect a new type of quasiparticle: so-called Rarita-Schwinger fermions.
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.
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.
Electronics should get smaller, faster, and above all more energy-efficient. These themes are also present in several research groups at PSI. From incremental improvements to complete rethinking – who is currently working on what?
In a trio of recent papers, a research group from the University of Zürich has made a number of new discoveries about the nature of cuprates' electronic structure and orbital composition. The results have important implications for superconductivity and pseudogaps in cuprates, and even the existence of type-II Dirac fermions in oxides.