'Sudden death' discovery challenges our understanding of superconductivity: ScienceAlert

Quantum chaos vortices that spontaneously appear in atomically thin layers of insulating materials have puzzled physicists, requiring revisions to models that could solve some pressing problems in the quest to understand superconductivity.

Experimental physicists from Princeton University in the US and Japan's National Institute of Materials Science have examined the spontaneous appearance of quantum fluctuations at the transition point from an electron traffic jam to a superconducting highway crossing a 2D landscape.

“How one superconducting phase can be changed into another is an interesting area of ​​study.” He says Princeton physicist and senior author, Sanfeng Wu.

“We have been interested in this problem in thin, clean, single crystalline materials for a while.”

Electrons drifting along the copper wires behind the drywall have a hard time getting from point A to point B. Turn on your TV, and rush-hour madness unfolds in those wires, as electrons swerve and collide, honking their little electronic horns and shaking their little electrons. Electronic handpieces overheat their tiny electronic motors.

Superconductivity is the dream. It's an easy ride from start to finish. No heat or energy wasted. It's as efficient as can be, perfect for generating powerful electromagnetic fields or high-speed computing that won't melt into a puddle.

However, it is also not an easy phase of conductivity to produce. This happens when electrons lose their sense of individuality and fall into a state of synchronization, forming what is known as Cooper pairsAble to negotiate the atomic neighborhood with Zen-like ease.

This requires a level of coolness that can only be achieved with some heavy and impressive equipment. However, if researchers can understand precisely what triggers this quantum shift and the role temperature plays, they may be able to settle for less cooling.

One area of ​​research involves examining the quantum behavior of electrons trapped on physically 2D surfaces. Since they are deprived of the ability to move up and down, quantum phenomena make their transition to a superconducting state more difficult.

“When you go to lower dimensions, the fluctuations become so strong that they kill any possibility of superconductivity.” He says Princeton physicist Nay Phuan Ong.

The fundamental killer of the electron's Zen state is best described as a quantum vortex. Or as ong describes it“Quantum versions of the vortex that appears when a bathtub drains.”

According to what is known as BKT transmissionafter Nobel laureates Vadim Berezinsky, John Kosterlitz, and David Thewlis These deadly death vortexes disappear in 2D materials when the temperature gets low enough.

By studying this space of quantum tornadoes that cause chaos in superconducting states, Wu and his team created a single layer of the semi-metallic tungsten ditelluride, which at anything warmer than absolute zero becomes an energy-suffocating insulator.

However, pumping enough electrons forces the current to flow in a superconducting manner.

However, the researchers noticed something quite strange when the temperature dropped. By adding enough electrons, you get superconductivity. However, at a critical level of electron movement, the whirlwinds of quantum madness return, shutting down the current.

Measurement of the vortices revealed that they were not ordinary quantum vortices, but rather remained stable at higher temperatures and magnetic fields than theory dictates. When the number of electrons drops below a certain amount, the vortices suddenly disappear.

“We expected to see strong fluctuations persisting below the critical electron density on the non-superconducting side, just like the strong fluctuations seen well above the BKT transition temperature.” He says Woo.

“However, what we found is that the vortex signals 'suddenly' disappear the moment the critical electron density is exceeded. This was a shock. We cannot explain this observation at all – the 'sudden death' of fluctuations.”

New paradigms offer possibilities for new methods of research that may lead to new technology. Given the potential benefits of developing room-temperature superconductivity, it is useful to have a good map of the weather on the quantum landscape.

This research was published in Nature physics.