Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Long-sought chiral anomaly detected in crystalline material

04.09.2015

A study by Princeton researchers presents evidence for a long-sought phenomenon -- first theorized in the 1960s and predicted to be found in crystals in 1983 -- called the "chiral anomaly" in a metallic compound of sodium and bismuth. The additional finding of an increase in conductivity in the material may suggest ways to improve electrical conductance and minimize energy consumption in future electronic devices.

"Our research fulfills a famous prediction in physics for which confirmation seemed unattainable," said N. Phuan Ong, Princeton's Eugene Higgins Professor of Physics, who co-led the research with Robert Cava, Princeton's Russell Wellman Moore Professor of Chemistry. "The increase in conductivity in the crystal and its dramatic appearance under the right conditions left little doubt that we had observed the long-sought chiral anomaly."


This sketch illustrates the notion of handedness, or chirality, which is found throughout nature. Most chemical structures and many elementary particles come in right- and left-handed forms.

Credit: Princeton University

The study was published online today in the journal Science.

The chiral anomaly - which describes how elementary particles can switch their orientation in the presence of electric and magnetic fields - stems from the observation that right- and left-handedness (or "chirality" after the Greek word for hand) is ubiquitous in nature. For example, most chemical structures and many elementary particles come in right- and left-handed forms that are mirror images of each other.

Early research leading up to the discovery of the anomaly goes back to the 1940s, when Hermann Weyl at the Institute for Advanced Study in Princeton, New Jersey, and others, discovered that all elementary particles that have zero mass (including neutrinos, despite their having an extremely small mass) strictly segregate into left- and right-handed populations that never intermix.

A few decades later, theorists discovered that the presence of electric and magnetic fields ruins the segregation of these particles, causing the two populations to transform into each other with observable consequences.

This field-induced mixing, which became known as the chiral anomaly, was first encountered in 1969 in work by Stephen Adler of the Institute for Advanced Study, John Bell of the European Organization for Nuclear Research (CERN) and Roman Jackiw of the Massachusetts Institute of Technology, who successfully explained why certain elementary particles, called neutral pions, decay much faster -- by a factor of 300 million -- than their charged cousins. Over the decades the anomaly has played an important if perplexing role in the grand quest to unify the four fundamental forces of nature.

The prediction that the chiral anomaly could also be observed in crystals came in 1983 from physicists Holger Bech Nielsen of the University of Copenhagen and Masao Ninomiya of the Okayama Institute for Quantum Physics. They suggested that it may be possible to detect the anomaly in a laboratory setting, which would enable researchers to apply intense magnetic fields to test predictions under conditions that would be impossible in high-energy particle colliders.

Recent progress in the development of certain kinds of crystals known as "topological" materials has paved the way toward realizing this prediction, Ong said. In the crystal of Na3Bi, which is a topological material known as a Dirac semi-metal, electrons occupy quantum states which mimic massless particles that segregate into left- and right-handed populations.

To see if they could observe the anomaly in Na3Bi, Jun Xiong, a graduate student in physics advised by Ong, cooled a crystal of Na3Bi grown by Satya Kushwaha, a postdoctoral research associate in chemistry who works with Cava, to cryogenic temperatures in the presence of a strong magnetic field that can be rotated relative to the direction of the applied electrical current in the crystal. When the magnetic field was aligned parallel to the current, the two chiral populations intermixed to produce a novel increase in conductivity, which the researchers call the "axial current plume." The experiment confirmed the existence of the chiral anomaly in a crystal.

"One of the key findings in the experiment is that the intermixing leads to a charge current, or axial current, that resists depletion caused by scattering from impurities," Ong said. "Understanding how to minimize the scattering of current-carrying electrons by impurities -- which causes electronic devices to lose energy as heat -- is important for realizing future electronic devices that are more energy-efficient. While these are early days, experiments on the long-lived axial current may help us to develop low-dissipation devices."

Media Contact

Catherine Zandonella
czandone@princeton.edu
609-258-0541

 @Princeton

http://www.princeton.edu 

Catherine Zandonella | EurekAlert!

More articles from Materials Sciences:

nachricht Move over, Superman! NIST method sees through concrete to detect early-stage corrosion
27.04.2017 | National Institute of Standards and Technology (NIST)

nachricht Control of molecular motion by metal-plated 3-D printed plastic pieces
27.04.2017 | Ecole Polytechnique Fédérale de Lausanne

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>