Axion particle spotted in solid-state crystal

Axion particle spotted in solid-state crystal
The scheme of a Weyl-semimetal-based axion insulator. Credit: Johannes Gooth

Scientists at the Max Planck Institute for Chemical Physics of Solids in Dresden, Princeton University, the University of Illinois at Urbana-Champaign, and the University of the Chinese Academy of Sciences have spotted a famously elusive particle: The axion, first predicted 42 years ago as an elementary particle in extensions of the standard model of particle physics. The results of the experiments are published in Nature.

The team found signatures of particles composed of Weyl-type electrons (Weyl fermions) in the correlated Weyl semimetal (TaSe4)2I. At , (TaSe4)2I is a one-dimensional crystal in which is conducted by Weyl fermions. However, by cooling (TaSe4)2I down below -11 degrees C, these Weyl fermions themselves condense into a crystal, a so-called "charge density wave," which distorts the underlying crystal lattice of the atoms. The initially free Weyl fermions are now localized and the initial Weyl semimetal (TaSe4)2I becomes an axion insulator. Similar to the existence of free electrons in metallic atomic crystals, the Weyl semimetal-based charge-density-wave crystal hosts axions that can conduct electrical current. However, such axions behave quite differently from electrons. When exposed to parallel electric and magnetic fields, they produce an anomalous positive contribution to the magnetoelectric conductivity.

Based on predictions from Andrei Bernevig's group at Princeton University, the group of Claudia Felser in Dresden produced the charge density wave Weyl metalloid (TaSe4)2I and investigated the electrical conduction in this material under the influence of electric and magnetic fields. The researchers found that the electric current in this material below -11 degrees C is actually carried by axion particles. "It's very surprising that materials that we think we know are suddenly showing such interesting quantum particles," says Claudia Felser, one of the lead authors of the paper.

Examining the novel properties of axion particles in table-top experiments could allow scientists to better understand the mysterious realm of quantum particles, and open up the field of highly correlated topological materials. "Another building block to my lifelong dream of realizing ideas from astronomic and high-energy physics with table-top experiments in solids," says Johannes Gooth.

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More information: J. Gooth et al, Axionic charge-density wave in the Weyl semimetal (TaSe4)2I, Nature (2019). DOI: 10.1038/s41586-019-1630-4
Journal information: Nature

Provided by Max Planck Society
Citation: Axion particle spotted in solid-state crystal (2019, October 8) retrieved 20 October 2019 from
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User comments

Oct 08, 2019
So, is this a kind of quasiparticle, or is this the same "axion" as the one that's a dark matter candidate?

Oct 08, 2019
It's the one that might be dark matter. And they're very light and small; we appear to be zeroing in on the solution to the dark matter puzzle. This would explain why we can't detect dark matter with heavy nuclei. We were looking in the wrong place.

Oct 08, 2019
In case it's not clear, this one may actually be a ground-breaking experiment and the detection of dark matter. It's getting bookmarked by me. This is the first smell of anything that looks like dark matter. It will take a while to confirm, but you may be looking at a Nobel Prize in Physics item here.

Oct 08, 2019
This is very exciting.

"If axions have low mass, thus preventing other decay modes (since there's no lighter particles to decay into), theories[which?] predict that the universe would be filled with a very cold Bose–Einstein condensate of primordial axions. Hence, axions could plausibly explain the dark matter problem of physical cosmology."

Oct 08, 2019
That would be nice, but my guess is that it is only a tiny fraction of dark matter, just like neutrinos.

Oct 08, 2019
Yes, this is AN axion, a pseudo-particle with properties homologous to the conjectured elementary particle yet to be found. From an early draft:

"Axions refer to elementary particles that have long been known in quantum field theory [1,2] but have yet to be observed in nature. However, it has been recently understood that axions can emerge as collective electronic excitations in certain crystals, so-called axion insulators."


So no, this is not THE axion. The Planck Society writer(s) are bafflingly misinformed:
"...have spotted a famously elusive particle: The axion, first predicted 42 years ago as an elementary particle in extensions of the standard model of particle physics."

Oct 08, 2019
Hmmmmm. I note that electrons also behave as so-called pseudo-particles in the Weyl metal under study. I think you might want to read the paper a bit more before you make a judgement.

Oct 09, 2019
"... It will take a while to confirm, but you may be looking at a Nobel Prize in Physics item here."

oh DS, SNAP!

you just bitch slapped all the woomongers into falling to their knees
shaking their fists at the uncaring heavens
screeching their outrage
that the Real Sciences of Time & Space
have left the fakirs groveling in their styes

blubbering of how unfair it is that their obsolete whackyness
using ouiija boards for their fake experiments

will never gain them a Nobel Prize
without active intervention
with violent threats
by pimp putin & whore trump

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