Scientific Highlights

22 September 2020
Thorsten Schmitt (links) und Milan Radovic an ihrer Experimentierstation an der Synchrotron Lichtquelle Schweiz SLS.

Customising an electronic material

Media Releases Research Using Synchrotron Light Materials Research Matter and Material

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.

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9 July 2020
Chern Number

Cherned up to the maximum

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.

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24 February 2020

Emergence of Nontrivial Low-Energy Dirac Fermions in Antiferromagnet EuCd2As2

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.

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12 July 2019
Weyl fermions

Weyl fermions discovered in another class of materials

Media Releases Matter and Material Materials Research Research Using Synchrotron Light

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.

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7 May 2019
Teaserbild Schröter Niels

New material also reveals new quasiparticles

Media Releases Matter and Material Materials Research Research Using Synchrotron Light

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.

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3 May 2019
Type-II Weyl semimetal WP2

New study gives compelling evidence that tungsten diphosphide is a type-II Weyl semimetal

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.

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15 February 2019

Watching electrons and switching bits on

Micro- and Nanotechnology Energy and Environment Matter and Material Materials Research Industrial co-operation Research Using Synchrotron Light Research Using Neutrons

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?

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22 October 2018
Electronic structure of overdoped La1.77Sr0.23CuO4. (left) dx2-y2 and dz2 band structure 
along the nodal direction. (middle) Light polarization analysis of the dx2-y2 and dz2 bands.
(right) Anti-nodal Fermi surface warping along the kz direction.

Cuprate Trilogy

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.

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