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New research suggests that a previously unknown quantum particle equivalent to a neutral electron might just have been discovered in a new state of matter.

Tungsten Filament
(Photo: Yakushev.dim / Wikimedia Commons)
Tungsten is used in the production of lighting lamps like an incandescent filament. Inert gases are used in inert lamps because tungsten oxidizes quickly in the open air when exposed to high temperature.

The chargeless particle isn't a fundamental building block of matter but is a quasiparticle that comes out from a collective behavior when the right conditions are met. In a new study, conditions were observed via sheets of semi-metallic crystals that showed perplexing electromagnetic behavior.

Sanfeng Wu, senior author and a physicist from Princeton University, says, "if our interpretation is correct, we see a new form of quantum matter." 

The study was published in the journal Nature on January 4th,

Understanding the 'Neutral Electron' Quantum Particle

Together with colleagues, Wu tried to follow up on findings from previous experiments that showed unique behavior in thin crystalline sheets of tungsten ditelluride. It conducts electricity much like a bulk of metal while being a strong insulator.

Researchers exposed the monolayer to various magnetic fields at low temperatures, where quantum effects are more pronounced and easier to measure how it will resist the electric current.

Regular materials showed to exhibit distinct behavior under the previously stated conditions. Wu explains that the quantum oscillation that occurs is due to the material's electrons shifting from the typical classical state and quantum mechanical state caused by circular motions in the magnetic field.

On the other hand, insulators are known not to show any quantum oscillations, which surprised scientists.  

"This came as a complete surprise. We don't fully understand it yet," says Wu.

Quantum Oscillation Explained

Roughly a century ago, physicists discovered quantum oscillations. Metals often have low resistance where their outermost electrons are not as tightly bound within the parent atoms. This is why metal allows electrons to flow and conduct electric currents.

It is common knowledge that strong magnetic fields could cause the electrons in metals to shift between normal classical states and circular quantum mechanical states. This causes oscillations in the resistivity of the metals.

On the other hand, electrons insulating materials are unable to move. Hence they do not conduct electric current and cannot show quantum oscillations no matter the magnetic field's strength.

This is why Wu and his colleagues were puzzled by the quantum oscillations observed from the tungsten ditelluride, a supposed-insulating monolayer.

New State of Matter

Physics today cannot explain the discovery made by researchers where the team hypothesizes that previously unknown forms of quantum matter cause the results.

Researchers believe that quantum oscillations could be explained further by quasiparticles, unseen, that aris from fixed electrons when the monolayer is exposed to a strong magnetic field. 

Wu also suggests that the so-called quasiparticle is a "neutral fermion" or an electron equivalent with no electric charge. He adds that the team is currently looking to test the hypothesis on neutral fermions further in tungsten ditelluride and other insulators to develop quantum oscillations.

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