‘Light-speed’ electrons discovered moving in 4 dimensions for the first time: ScienceAlert

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By journalsofus.com

Elusive behavior of electrons from the most mundane electronic activity has finally been isolated in a real-world material.

A team of physicists led by Ryuhei Oka of Ehime University has measured what are known as Dirac electrons in a superconducting polymer called bis(ethylenedithio)-tetrathiafulvalene. These are electrons that exist in conditions that effectively make them massless, allowing them to behave more like photons and oscillate at the speed of light.

This discovery, the researchers say, will allow for a better understanding of topological materials: quantum materials that behave as an electronic insulator on the inside and a conductor on the outside.

Superconductors, semiconductors and topological materials are gaining relevance, especially due to their possible applications in quantum computers. But there is still a lot we don’t know about these materials and their behavior.

Dirac electrons refer to ordinary old electrons found in extraordinary conditions that require a dose of special relativity to understand quantum behaviors. Here, the overlapping of atoms places some of their electrons in a strange space that allows them to jump between materials with excellent energy efficiency.

Formulated from the equations of theoretical physicist Paul Dirac almost a century ago, we now know that they exist: they have been detected in grapheneas well as other topological materials.

However, to harness the potential of Dirac electrons we need to understand them better, and this is where physicists run into a problem. Dirac electrons coexist with standard electrons, which means that detecting and measuring one type is very difficult to do unambiguously.

Oka and his colleagues found a way to do this by taking advantage of a property called electron spin resonance. Electrons are charged particles that spin; This rotating distribution of charge means that each exhibits a magnetic dipole. So when a magnetic field is applied to a material, it can interact with the spins of any unpaired electrons it contains, altering its spin state.

This technique can allow physicists to detect and observe unpaired electrons. And, as Oka and the other researchers discovered, it can also be used to directly observe the behavior of Dirac electrons in bis(ethylenedithio)-tetrathiafulvalene, distinguishing them from standard electrons as different spin systems.

The team discovered that to fully understand it, the Dirac electron needs to be described in four dimensions. There are the three standard spatial dimensions, the x, y and z axes; and then there is the energy level of the electron, which constitutes a fourth dimension.

“Since three-dimensional band structures cannot be represented in four-dimensional space,” The researchers explain in their article“The analysis method proposed here provides a general way of presenting important and easy-to-understand information about such band structures that cannot be obtained in any other way.”

By analyzing the Dirac electron based on these dimensions, the researchers were able to discover something we didn’t know before. The speed of its movement is not constant; rather, it depends on the temperature and the angle of the magnetic field within the material.

This means we now have another piece of the puzzle to help us understand the behavior of Dirac electrons, a piece that can help harness their properties in future technology.

The team’s research has been published in Materials Advances.

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