News

When Dirac meets frustrated magnetism

The fields of condensed matter physics and material science are intimately linked because new physics is often discovered in materials with special arrangements of atoms. Crystals, which have repeating units of atoms in space, can have special patterns which result in exotic physical properties. Particularly exciting are materials which host multiple types of exotic properties because they give scientists the opportunity to study how those properties interact with and influence each other. The combinations can give rise to unexpected phenomena and fuel years of basic and technological research.

advertisement

In a new study published in Science Advances this week, an international team of scientists from the USA, Columbia, Czech Republic, England, and led by Dr. Mazhar N. Ali at the Max Planck Institute of Microstructure Physics in Germany, has shown that a new material, KV3Sb5, has a never-seen-before combination of properties that results in one of the largest anomalous Hall effects (AHEs) ever observed; 15,500 siemens per centimeter at 2 Kelvin.

Discovered in the lab of co-author Prof. Tyrel McQueen at Johns Hopkins University, KV3Sb5 combines four properties into one material: Dirac physics, metallic frustrated magnetism, 2D exfoliability (like graphene), and chemical stability.

Dirac physics, in this context, relates to the fact that the electrons in KV3Sb5 aren t just your normal run-of-the-mill electrons; they are moving extremely fast with very low effective mass. This means that they are acting "light-like"; their velocities are becoming comparable to the speed of light and they are behaving as though they have only a small fraction of the mass which they should have. This results in the material being highly metallic and was first shown in graphene about 15 years ago.

The "frustrated magnetism" arises when the magnetic moments in a material (imagine little bar magnets which try to turn each other and line up North to South when you bring them together) are arranged in special geometries, like triangular nets. This scenario can make it hard for the bar magnets to line up in way that they all cancel each other out and are stable. Materials exhibiting this property are rare, especially metallic ones. Most frustrated magnet materials are electrical insulators, meaning that their electrons are immobile. "Metallic frustrated magnets have been highly sought after for several decades. They have been predicted to house unconventional superconductivity, Majorana fermions, be useful for quantum computing, and more," commented Dr. Ali.

Structurally, KV3Sb5 has a 2D, layered structure where triangular vanadium and antimony layers loosely stack on top of potassium layers. This allowed the authors to simply use tape to peel off a few layers (a.k.a. flakes) at a time. "This was very important because it allowed us to use electron-beam lithography (like photo-lithography which is used to make computer chips, but using electrons rather than photons) to make tiny devices out of the flakes and measure properties which people can t easily measure in bulk." remarked lead author Shuo-Ying Yang, from the Max Planck Institute of Microstructure Physics. "We were excited to find that the flakes were quite stable to the fabrication process, which makes it relatively easy to work with and explore lots of properties."

Armed with this combination of properties, the team first chose to look for an anomalous Hall effect (AHE) in the material. This phenomenon is where electrons in a material with an applied electric field (but no magnetic field) can get deflected by 90 degrees by various mechanisms. "It had been theorized that metals with triangular spin arrangements could host a significant extrinsic effect, so it was a good place to start," noted Yang. Using angle resolved photoelectron spectroscopy, microdevice fabrication, and a low temperature electronic property measurement system, Shuo-Ying and co-lead author Yaojia Wang (Max Planck Institute of Microstructure Physics) were able to observe one of the largest AHE s ever seen.

These results may also help scientists identify other materials with this combination of ingredients. "Importantly, the same physics governing this AHE could also drive a very large spin Hall effect (SHE) -- where instead of generating an orthogonal charge current, an orthogonal spin current is generated," remarked Wang. "This is important for next-generation computing technologies based on an electron s spin rather than its charge."

"This is a new playground material for us: metallic Dirac physics, frustrated magnetism, exfoliatable, and chemically stable all in one. There is a lot of opportunity to explore fun, weird phenomena, like unconventional superconductivity and more," said Ali, excitedly.

Materials provided by Max-Planck-Institute for Microstructure Physics . Note: Content may be edited for style and length.

Max-Planck-Institute for Microstructure Physics. "When Dirac meets frustrated magnetism." ScienceDaily. ScienceDaily, 31 July 2020. .

Max-Planck-Institute for Microstructure Physics. "When Dirac meets frustrated magnetism." ScienceDaily. www.sciencedaily.com/releases/2020/07/200731145141.htm (accessed July 31, 2020).

advertisement

1

July 6, 2020 — Researchers report that they have observed a quantum fluid known as the fractional quantum Hall states (FQHS), one of the most delicate phases of matter, for the first time in a monolayer 2D ...

July 9, 2019 — Researchers have developed a novel technique that could enable new technologies that use properties of quantum physics for computing, communication and sensing, which may lead to ...

Nov. 9, 2017 — The US Department of Energy s Ames Laboratory has discovered and described the existence of a unique disordered electron spin state in a metal that may provide a unique pathway to finding and ...

Oct. 13, 2017 — A new method that precisely measures the mysterious behavior and magnetic properties of electrons flowing across the surface of quantum materials could open a path to next-generation electronics. A ...
Read more on sciencedaily.com
News Topics :
RELATED STORIES :
Technology
Since then, scientists have found more exotic topological phases including Dirac semimetals, Weyl semimetals and Axionic insulators. But most recently, materials that are insulating in the bulk, on surfaces and...
Technology
Scientists have manipulated the magnetic and crystalline properties of chromium triiodide to create the world s first 2D magnet. This could help us to further explore the 2D world and...
Technology
These materials magnetic Weyl semi metals are innately quantum but bridge the two worlds of topology and spintronics. Topological materials exhibit strange properties including super fast electrons that travel without...
Technology
A newly identified insulating material using the symmetry principles behind wallpaper patterns may provide a basis for quantum computing, according to an international team of researchers. This strontium lead sample Sr2Pb3...
Technology
An international team of researchers led by scientists at Princeton University has found that a magnetic material at room temperature enables electrons to behave counterintuitively, acting collectively rather than as...