Physics

Massless particle discovery could radically accelerate electronics

Scientists lead by Princeton professor M. Zahid Hasan have discovered the Weyl fermion, a particle theorized more than 85 years ago that may open up whole new areas of high-speed electronics and quantum computing
Scientists lead by Princeton professor M. Zahid Hasan have discovered the Weyl fermion, a particle theorized more than 85 years ago that may open up whole new areas of high-speed electronics and quantum computing
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Researchers from Princeton's Department of Physics, (from left to right) graduate students Ilya Belopolski and Daniel Sanchez; postdoctoral research associate Guang Bian, professor of physics M. Zahid Hasan, and associate research scholar Hao Zheng.
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Researchers from Princeton's Department of Physics, (from left to right) graduate students Ilya Belopolski and Daniel Sanchez; postdoctoral research associate Guang Bian, professor of physics M. Zahid Hasan, and associate research scholar Hao Zheng.
Scientists lead by Princeton professor M. Zahid Hasan have discovered the Weyl fermion, a particle theorized more than 85 years ago that may open up whole new areas of high-speed electronics and quantum computing
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Scientists lead by Princeton professor M. Zahid Hasan have discovered the Weyl fermion, a particle theorized more than 85 years ago that may open up whole new areas of high-speed electronics and quantum computing
A detector image signals the existence of Weyl fermions. The positive and negative signs denote whether the particle's spin is in the same direction as its motion
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A detector image signals the existence of Weyl fermions. The positive and negative signs denote whether the particle's spin is in the same direction as its motion

An exotic particle theorized more than 85 years ago has finally been discovered. Dubbed the "Weyl fermion", it is a strange but stable particle that has no mass, behaves as both matter and anti-matter inside a crystal, and is claimed to be able to create completely massless electrons. Scientists believe that this new particle may result in super-fast electronics and significant inroads into novel areas of quantum computing.

There aretwo types of particles that make up the universe and everything in it: fermionsand bosons. In simple terms, fermions are all the particles that make up matter(for example, electrons), and bosons are all the particles that carry force(for example, photons). Ordinarily, fermions such as electrons can collide witheach other, losing energy, and no two fermions can share the same state at the sameposition at the same time. Weyl fermions being massless, however, have no suchrestrictions.

Weyl fermions were firstmooted in 1929 by physicist and mathematician Hermann Weyl, who theorized thatmassless fermions able to carry an electric charge could exist. Without mass,he believed, electrons created from Weyl fermions would be able to moveelectric charge in a circuit much more quickly than ordinary electrons. Infact, according to this latest research, electric current carried by Weyl electronsin a test medium is able to move at least twice as fast as that carried byelectrons in graphene and at least 1,000 times faster than in ordinarysemiconductors.

Researchers from Princeton's Department of Physics, (from left to right) graduate students Ilya Belopolski and Daniel Sanchez; postdoctoral research associate Guang Bian, professor of physics M. Zahid Hasan, and associate research scholar Hao Zheng.
Researchers from Princeton's Department of Physics, (from left to right) graduate students Ilya Belopolski and Daniel Sanchez; postdoctoral research associate Guang Bian, professor of physics M. Zahid Hasan, and associate research scholar Hao Zheng.

The international team led by Princeton University scientists used the PrincetonInstitute for the Science and Technology of Materials (PRISM) andLaboratory for Topological Quantum Matter and Spectroscopy to look into manydozens of crystal arrangements before alighting upon the asymmetrical tantalumarsenide crystal (a semi-metalthat has the properties of both a conductor and an insulator) asa prime candidate in the hunt for the theorized particle.

Over-sized crystals of the tantalum arsenide were firstplaced in a scanning tunneling spectromicroscope cooled to near absolute zero todetermine if they matched the hypothetical specifications for accommodatinga Weyl fermion. Then, once the crystals had passed that test, the team took themto the Lawrence Berkeley National Laboratory in California where high-energy photonbeams fired from a particle accelerator were shone through them. This testfinally confirmed the presence of the existence of the long sought after Weylfermion.

"Thenature of this research and how it emerged is really different and moreexciting than most of other work we have done before," said Su-Yang Xu, apostdoctoral research associate at Princeton. "Usually, theorists tell usthat some compound might show some new or interesting properties, then we asexperimentalists grow that sample and perform experiments to test theprediction. In this case, we came up with the theoretical prediction ourselvesand then performed the experiments. This makes the final success even moreexciting and satisfying than before."

A detector image signals the existence of Weyl fermions. The positive and negative signs denote whether the particle's spin is in the same direction as its motion
A detector image signals the existence of Weyl fermions. The positive and negative signs denote whether the particle's spin is in the same direction as its motion

As a quasiparticle – that is, a particle that exists inside a solid (inthis instance) but acts as if it were a weakly interacting particle in freespace – the Weyl fermion is massless and has a high degree ofmobility. This is because, as the particle's spin is both in the same direction as itsmotion (known in physics as "right-handed") and in the opposite direction in which it moves ("left-handed"), it is able to traversethrough and around obstacles that impede ordinary electrons.

"It'slike they have their own GPS and steer themselves without scattering,"said Princeton University physicist Zahid Hasan, who lead the research team."They will move and move only in one direction since they areeither right-handed or left-handed and never come to an end because they justtunnel through. These are very fast electrons that behavelike unidirectional light beams and can be used for new types of quantumcomputing."

Weyl originally posited hisfermion as part of an alternate model to the theory of relativity proposed byhis associate Albert Einstein. And, though Weyl's hypothesis lost out toEinstein’s, the idea of his theoretical particle continuedto tantalize physicists for many years afterward. However, as a merely "theoretical" particle, even when inklings of the Weyl fermion were uncovered over the decades, they were mistakenly thought to be evidence of neutrinos. In hindsight, the evidence was actually for Weyl fermions, for in 1998 neutrinos were actually discovered to have a small amount of mass.

"People figured that although Weyl's theory was not applicable torelativity or neutrinos, it is the most basic form of fermion and had all otherkinds of weird and beautiful properties that could be useful," said Hasan."After more than 80 years, we found that this fermion was already there,waiting. It is the most basic building block of all electrons. It is excitingthat we could finally make it come out following Weyl's 1929 theoreticalrecipe."

The team included researchers from Princeton's Department of Physics, Peking University, the National Taiwan University, the National University of Singapore, Oak Ridge National Laboratory; and Northeastern University.

The results of this work were recently published in the journal Science.

Source: Princeton University

14 comments
quax
Best account on a popular science site I've seen yet. Much better than phys.org for instance. Most science journo's don't even seem to grasp the difference between a elementary and a quasi-particle. Kudos!
Michiel Mitchell
and these mass-less electrons... what would those be made up of... this could mean that anything can be made mass-less.... Sweet!!!!
Brian M
Confusing, ok a fermion makes up matter so has mass, and a boson carries force, got that. However Weyl fermions have no mass, and can make up massless electrons. If they have no mass but presumable have force due to having a charge, aren't they bosons rather than fermions? Maybe I need to hit the physics books!
Robert in Vancouver
Thankfully, real scientists never say 'the science is settled'. If they did, they would never look for or find particles like the Wyel. Infact, real scientists are still studying, testing, and questioning the theory of gravity and other theories that most people consider as 'settled science.'
tsvieps
If it is massless and barely interacts, how is it useful for computing or memory devices? Photons are massless, but have momentum and energy. These Weyl fermions sound similar in some ways. But are photons used in computer devices? Photons certainly are used in communication devices as they can be created in bunches as pulses and then detected. But the article was not clear for me on how Weyl fermions can be used in a practical way, even if they can help us better understand the substructure of electrons.
BillyMayfield
this is the missing particle i need for my transporter beam. i need larger dylithium crystal.convert my fermions into wyels them shoot them on a bosom then reconvert into fermions. i am transported.
NoahCowper
dose this have any thing to do with Tesla's experiments and transmitting electricity instantly or 500 times faster then the speed of light?
quax
Oh well, based on the comments here, the concept of quasi-particle is nevertheless not sinking in at all. These are not "massless" electrons. These things are excitations in the crystal structure that allow electrons to shed resistive mass (i.e. the additional drag caused by the surrounding matter). Quasi-particles obey the same quantum mechanical laws as the real thing but are collective interaction phenomena.
Kpar
Billy Mayfield..."shoot them on a bosom"... really? I'm not sure which website you think you are on. Quax... I was wondering... "electrons created from Weyl fermions"... is there a new kind (or species) of electron? I must have missed that- of course, now that I am in my dotage, maybe I just forgot....
starship
"massless" - does this mean 'no substance' as in 'non-materiality'? Plato argued for non-material substance which was non-extended. Others have argued for non-material substances that were extended. Today science (and philosophy) I think would not even consent to the concept of non-materiality (except maybe around coffee-table discussions where everything goes).