Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The marriage of topology and magnetism in a Weyl system

06.08.2018

Topology is a global aspect of materials, leading to fundamental new properties for compounds with large relativistic effects. The incorporation of heavy elements give rise to non-trivial topological phases of matter, such as topological insulators, Dirac and Weyl semimetals. The semimetals are characterized by band-touching points with linear dispersion, similar to massless relativistic particles in high energy physics.

The interplay of symmetry, relativistic effects and, in magnetic materials, the magnetic structure, allows for the realization of a wide variety of topological phases through Berry curvature design. The Berry curvature describes the entanglement of the valence and conduction bands in an energy band structure.


The marriage of topology and magnetism in a Weyl system

MPI CPfS

Weyl points and other topological electronic bands can be manipulated by various external perturbations (magnetic field, pressure …), which results in exotic local properties such as the chiral or gravitational anomaly, and large topological Hall effects, concepts which were developed in other fields of physics such as high energy physics and astrophysics.

Weyl semimetals require broken inversion crystal symmetry or time-reversal symmetry (via magnetic order or an applied magnetic field). So far, no intrinsic magnetic Weyl semimetals with Weyl nodes close to the Fermi energy were realized.

In the recent study, scientists from the Max Planck Institute for Chemical Physics of Solids in Dresden, in collaboration with the Technische Universität Dresden, scientists from Beijing, Princeton, Oxford, and others found evidence for Weyl physics in the magnetic Shandites Co3Sn2S2.

The family of Shandite crystals contain transition metals on a quasi 2-dimensional Kagome lattice that can give rise to magnetism. One of the most interesting is Co3Sn2S2 which has the highest magnetic ordering temperature within this family and in which the magnetic moments on the Co atoms are aligned in a direction perpendicular to the Kagome plane.

The observation of the quantum anomalous Hall effect at room temperature would allow for novel computing technologies including quantum computing. To realize this possibility, our strategy is (i) to search for quasi two-dimensional magnetic materials with topological band structures and (ii) to synthesis these materials as monolayers or very thin films.

However, so far no magnetic materials are known, which could lead to higher temperature quantum anomalous Hall effect. In order to obtain large Hall angles, namely the ratio of the Hall to the electrical conductivities, two conditions must be satisfied: firstly a large Hall conductivity and secondly a small number of carriers. These conditions are met in Weyl semi-metals where the Weyl nodes are close in energy to the Fermi energy.

We have found that Co3Sn2S2 displays a giant anomalous Hall effect and a giant hall angle at temperatures of up to 150 K suggestive of a Weyl semimetal. Subsequent band structure calculations indeed show the presence of Weyl nodes close to the Fermi energy. Moreover, magnetotransport measurements give evidence for a chiral anomaly that is a clear signature of a Weyl semimetal. Our work provides a clear path to the observation of a quantum anomalous hall effect at room temperature by exploring families of magnetic Weyl semimetals.

This study, for the first time, realizes the giant anomalous Hall effects by using a magnetic Weyl semimetal, which establishes the magnetic Weyl semimetal candidate Co3Sn2S2 as a key class of materials for fundamental research and applications connecting the topological physics and spintronics.

With a long-range out-of-plane ferromagnetism on the Kagomé-lattice model for the platform of quantum topological states, we further expect that this material is an excellent candidate for observation of the quantum anomalous Hall state in the two-dimensional limit.

The research at the Max Planck Institute for Chemical Physics of Solids (MPI CPfS) in Dresden aims to discover and understand new materials with unusual properties.

In close cooperation, chemists and physicists (including chemists working on synthesis, experimentalists and theoreticians) use the most modern tools and methods to examine how the chemical composition and arrangement of atoms, as well as external forces, affect the magnetic, electronic and chemical properties of the compounds.

New quantum materials, physical phenomena and materials for energy conversion are the result of this interdisciplinary collaboration.

The MPI CPfS is part of the Max Planck Society and was founded in 1995 in Dresden. It consists of around 280 employees, of which about 180 are scientists, including 70 doctoral students.

Wissenschaftliche Ansprechpartner:

Prof. Dr. Claudia Felser, Enke Liu, PhD

Originalpublikation:

Giant anomalous Hall effect in a ferromagnetic kagome-lattice semimetal, Nature Physics, https://doi.org/10.1038/s41567-018-0234-5

Weitere Informationen:

https://www.cpfs.mpg.de/en

Dipl.-Übers. Ingrid Rothe | Max-Planck-Institut für Chemische Physik fester Stoffe

More articles from Physics and Astronomy:

nachricht 26AlF – the first detection of a radioactive molecule in space
31.07.2018 | Max-Planck-Institut für Radioastronomie

nachricht X-ray technology reveals never-before-seen matter around black hole
30.07.2018 | Hiroshima University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Concepts for new switchable plasmonic nanodivices

A magneto-plasmonic nanoscale router and a high-contrast magneto-plasmonic disk modulator controlled by external magnetic fields

Plasmonic waveguides open the possibility to develop dramatically miniaturized optical devices and provide a promising route towards the next-generation of...

Im Focus: 26AlF – the first detection of a radioactive molecule in space

The first unambiguous observation of a radioactive molecule, 26AlF, was made in the ancient nova-like object CK Vul (or Nova Vul 1670), which - most likely - is a stellar-merger remnant. The eruption of the object was observed between 1670-1672 in Europe. The interest in this object has been recently rejuvenated by the discovery of molecular gas of a very peculiar isotopic composition in the remnant.
The finding was announced by an international research team led by Tomasz Kamiński (CfA), including Karl Menten (MPIfR Bonn).

The variable star CK Vulpeculae (CK Vul) is known as the location of a stellar outbreak, a nova, which was observed by European astronomers in the 17th century...

Im Focus: Scientists create 'impossible' materials in simple way

Scientists from NUST MISIS and colleagues from the University of Bayreuth, the University of Münster (Germany), the University of Chicago (U.S.), and Linköping University (Sweden) have created nitrides, a material previously considered impossible to obtain. More amazing, they have shown that the material can be obtained using a very simple method of direct synthesis. Articles about the revolutionary research results have been published in Nature Communications and Angewandte Chemie International Edition.

Nitrides are actively used in superhard coatings and electronics. Usually, the nitrogen content in these materials is low, and it is therefore difficult to get...

Im Focus: World-first quantum computer simulation of chemical bonds using trapped ions

An international group of researchers has achieved the world’s first multi-qubit demonstration of a quantum chemistry calculation performed on a system of trapped ions, one of the leading hardware platforms in the race to develop a universal quantum computer.

The research, led by Cornelius Hempel and Thomas Monz, explores a promising pathway for developing effective ways to model chemical bonds and reactions using...

Im Focus: Growing brain cancer in a dish

For the first-time, researchers at IMBA- Institute of Molecular Biotechnology of the Austrian Academy of Sciences – develop organoids, that mimic the onset of brain cancer. This method not only sheds light on the complex biology of human brain tumors but could also pave the way for new medical applications.

Brain tumors are among the most aggressive and deadly cancers and a leading cause of cancer-related death in children and young adults.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

 
Latest News

UCLA-developed artificial intelligence device identifies objects at the speed of light

03.08.2018 | Information Technology

New lung cell type discovered

03.08.2018 | Life Sciences

Novel PET imaging method could track and guide therapy for type 1 diabetes

03.08.2018 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>