Nav: Home

Heusler, weyl and berry

October 10, 2018

Fritz Heusler (1866-1947), Hermann Weyl (1885-1955) and Michael Berry (1941-) are three renowned scientists whose work has led to new and important insights into materials science, topology and condensed-matter physics. These three fields of science have come together recently with the discovery of new and exciting quantum properties in new classes of material which could enable new science including computing technologies and catalysis.

Heusler is the name of the discoverer of mostly magnetic compounds that were of interest quite some time ago. But these compounds were recently found to host non-trivial topological properties that open a large field of novel physics. Hidden in the energy band structure of these materials are singular points that can be described with mathematical tools that originate from Weyl; these points are associated with the discovery of quasi-particles that are now called Weyl fermions. They are not found among the elementary particles of high energy physics, but we believe they exist in solid materials and determine their topology. The third name Berry stands for the measurable effects that reveal the physics at hand. Under certain well defined conditions there exists a vector field, similar to the magnetic field, called the Berry curvature. It determines the magnitude of a number of important effects, such as the anomalous Hall Effect and the Spin Hall Effect. It is the art of the experimentalist to suitably modify the materials in order to tune the Berry curvature and thus render the topology visible. In this review a great number of examples are given for various symmetry properties of Heusler compounds, a large class of materials that can easily be tuned to display ferromagnetic, antiferromagnetic, non-collinear or compensated magnetic order. These magnetic orderings give rise to pronounced electric and thermoelectric effects whose fingerprints are uncovered and explained including particle-like vortex spin structures, the antiskyrmions that are typical for a certain subset of Heusler compounds.

Considering the large number of existing inorganic compounds and the recently proposed large number of nonmagnetic topological materials, Heusler compounds serve as a model system for the understanding and impact of magnetism on topology. Breaking time reversal symmetry via magnetism or an external magnetic field can lead to even larger effects than in non-magnetic materials based on the large separation between Weyl points of different chiralities. Based on a systematic study of Heusler materials we predict that there are a huge number of magnetic topological materials awaiting to be discovered.

With regard to applications, the large Nernst effect and classical and quantum Hall effects around room temperature based on the high Curie temperatures of Heusler compounds and their relatives have the potential to have great impact in energy conversion and quantum electronic devices for spintronics or quantum computing.

Max Planck Institute for Chemical Physics of Solids

Related Magnetic Field Articles:

Understanding stars: How tornado-shaped flow in a dynamo strengthens the magnetic field
A new simulation based on the von-Kármán-Sodium (VKS) dynamo experiment takes a closer look at how the liquid vortex created by the device generates a magnetic field.
'Quartz' crystals at the Earth's core power its magnetic field
Scientists at the Earth-Life Science Institute at the Tokyo Institute of Technology report in Nature (Fen.
Brightest neutron star yet has a multipolar magnetic field
Scientists have identified a neutron star that is consuming material so fast it emits more x-rays than any other.
Confirmation of Wendelstein 7-X magnetic field
Physicist Sam Lazerson of the US Department of Energy's Princeton Plasma Physics Laboratory has teamed with German scientists to confirm that the Wendelstein 7-X fusion energy device called a stellarator in Greifswald, Germany, produces high-quality magnetic fields that are consistent with their complex design.
High-precision magnetic field sensing
Scientists have developed a highly sensitive sensor to detect tiny changes in strong magnetic fields.
Brilliant burst in space reveals universe's magnetic field
Scientists have detected the brightest fast burst of radio waves in space to date -- locating the source of the event with more precision than previous efforts.
Optical magnetic field sensor can detect signals from the nervous system
The human body is controlled by electrical impulses in the brain, the heart and nervous system.
What did Earth's ancient magnetic field look like?
New work from Carnegie's Peter Driscoll suggests Earth's ancient magnetic field was significantly different than the present day field, originating from several poles rather than the familiar two.
Just what sustains Earth's magnetic field anyway?
Earth's magnetic field shields us from deadly cosmic radiation, and without it, life as we know it could not exist here.
Ironing out the mystery of Earth's magnetic field
The Earth's magnetic field has been existing for at least 3.4 billion years thanks to the low heat conduction capability of iron in the planet's core.

Related Magnetic Field Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Failure can feel lonely and final. But can we learn from failure, even reframe it, to feel more like a temporary setback? This hour, TED speakers on changing a crushing defeat into a stepping stone. Guests include entrepreneur Leticia Gasca, psychology professor Alison Ledgerwood, astronomer Phil Plait, former professional athlete Charly Haversat, and UPS training manager Jon Bowers.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".