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Nov. 12 (UPI) – Scientists have discovered a new family of quasiparticles that defy textbook physics. The researchers found the particles, called Brown-Zak fermions, in graphene-based superlattices.
Physicists spotted the particles and their strange behavior – described Friday in the journal Nature Communications – after lining a single layer of graphene with an insulating sheet of boron nitride.
Typically, in the absence of a magnetic field, electrons travel in a straight line. When a magnetic field is applied, the electron paths begin to bend and the particles begin to move in circles.
“In a layer of graphene that has been aligned with the boron nitride, the electrons also start to bend, but if you set the magnetic field to specific values, the electrons move again in straight paths, as if it is no longer there. magnetic field, ”study co-author Piranavan Kumaravadivel said in a press release.
“This behavior is radically different from textbook physics,” said Kumaravadivel, a physicist at the University of Manchester in Britain.
The researchers hypothesized that the new electron behavior is activated by new quasiparticles, which form at particularly high magnetic field values.
“Those quasiparticles have their own unique properties and exceptionally high mobility despite the extremely high magnetic field,” said Alexey Berdyugin, study co-author and Manchester physicist.
For years, scientists have studied graphene-boron nitride superlattices to better understand and take advantage of a fractal pattern known as the Hofstadter butterfly.
The latest discovery forced physicists to reconsider everything they thought they knew about the fractal phenomenon.
“The concept of quasiparticles is undoubtedly one of the most important in condensed matter physics and quantum many-body systems,” said lead author Julien Barrier.
“It was introduced by theoretical physicist Lev Landau in the 1940s to describe collective effects as an” excitation of a particle. “They are used in a number of complex systems to account for the effects of many bodies,” said Barrier. also a physicist at the University of Manchester.
Until now, scientists thought that the behavior of electrons inside the graphene-boron nitride superlattices was dictated by Dirac fermions, photon-like quasiparticles that proliferate at high magnetic field values.
However, Dirac fermions failed to explain some of the unusual material properties of graphene-boron nitride superlattices.
Researchers suggest that Brown-Zak fermions are part of a family of quasiparticles that explain some of these mysterious properties.
In the lab, the researchers fabricated extremely large graphene-boron nitride super lattices, giving the material’s electrons greater mobility.
When the scientists supplied the super lattice with extremely high magnetic fields – 500,000 times the Earth’s magnetic field – electrons in circular motion began to travel in a straight line. The electrons were able to keep their paths in a straight line over the entire length of the super lattice sheets without dispersing.
Researchers suggest that such enormous electron mobility makes graphene-boron nitride superlattices an ideal material for creating ultra-high-frequency transistors, a key component in computer processors.
Greater electron mobility allows transistors to operate at higher frequencies, increasing the speed and efficiency with which they can power calculations.
“The findings are important, obviously for fundamental studies on electron transport, but we believe that understanding quasiparticles in new super lattice devices under high magnetic fields could lead to the development of new electronic devices,” Barrier said.
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