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Tuesday, 18 February 2020

Researchers have discovered new electronic state of matter

In this artist's view, electrons travel in cars in increasing numbers, giving rise to a series of conductances which appears in Pascal's triangle. | Yun-Yi Pai

In a metal or a semiconductor, the electrons move and disperse more or less freely, this movement can be determined by applying an electrical voltage to the material in question. Within ballistic conductors (materials with optimized electrical conductivity, in particular by the absence of collision between electrons), the electrons move almost like vehicles on a highway. The main advantage is that they do not emit heat and can be used in a unique way compared to ordinary electronics. Researchers have previously,  successfully designed this type of ballistic conductor. Recently, scientists have discovered a new electronic state of matter in which electrons move, without dispersing, in groups of two or more at a time rather than individually, as was the case so far in early ballistic conductors.

" Research is focused on measurements in one-dimensional conductive systems where electrons move without dispersing in groups of two or more at a time, rather than individually, " say Jeremy Levy, professor of condensed matter physics, and Patrick Irvin, Associate Research Professor. Both from the Department of Physics and Astronomy at the University of Pittsburgh are co-authors of the study, the results of which were published on February 14 in the journal Science .

"Normally, the electrons in semiconductors or metals move and disperse, and eventually drift in one direction if you apply voltage. But in ballistic conductors, electrons move more like cars on a highway (see title image). The advantage of this is that they do not give off heat and can be used in very different ways than what is done for ordinary electronics. Researchers before us had successfully created this type of ballistic conductor,” says Levy.



“Electron clusters” giving rise to new forms of electronic matter

"The discovery we made shows that when electrons can be made to attract each other, they can form pairs or clusters of three, four and five electrons, which literally behave like new types of particles, new forms of electronic matter,” he adds.

Levy compared the discovery to the way quarks bond to form neutrons and protons. An important clue to discover this new state of matter was to recognize that these ballistic conductors corresponded to a sequence in the Pascal triangle.

The first three lines of Pascal's triangle. Credits: Wikimedia

"If you look in different directions of Pascal's triangle, you can see different sequences of numbers, including the following: 1, 3, 6, 10, 15, 21. It is a sequence that we noticed in our data, it was therefore a difficult clue as to say what was really going on. The discovery took us a while to understand, but it was because we did not know, at the start, that we were looking at particles composed of an electron, two electrons, three electrons, etc. Together, they correspond to the sequence 1, 3, 6, 10”, explains Levy.

A link with quantum entanglement ...

Also director of the Pittsburgh Quantum Institute, Levy noted that the new particles have properties related to quantum entanglement, which can potentially be used for quantum computing and quantum redistribution. He notably declares that the discovery is an exciting advance towards the next stage of quantum physics.

"This research is part of a larger effort here in Pittsburgh to develop new science and technology related to the second quantum revolution," he said.

During the first quantum revolution, the scientific community realized that the world around us is fundamentally governed by the laws of quantum physics. This discovery made it possible, among other things, to understand the periodic table, the behavior of materials and helped the development of transistors, computers, MRI scanners and information technology in the broad sense.

"Now, in the 21st century, we examine all the strange predictions of quantum physics, we dissect them and use them. When we talk about applications, we think of quantum computing, quantum teleportation, quantum communications, quantum detection ... Ideas that exploit properties of the quantum nature of matter that have been ignored before," concludes Levy.



Directly published by Levy, the video below explains the study at three different levels of complexity:




Bibliography:

Pascal conductance series in ballistic one-dimensional LaAlO3/SrTiO3 channels

Megan Briggeman, Michelle Tomczyk, Binbin Tian, Hyungwoo Lee, Jung-Woo Lee, Yuchi H, Anthony Tylan-Tyler, Mengchen Huang, Chang-Beom Eom, David Pekker, Roger S. K. Mong, Patrick Irvin, Jeremy Levy

Science  14 Feb 2020:

Vol. 367, Issue 6479, pp. 769-772

DOI: 10.1126/science.aat6467

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