Groundbreaking Research: Quantum Vortices and Unconventional Superconducting Quantum Criticality in Single-Layer WTe2

2024-01-16 04:16:25

In a lab at Princeton University, a group of physicists are toying with a surprising new material—one that’s only three atoms thick but can switch from an insulator to a superconductor at will. Like a scientific version of magic, they discovered some completely unexpected quantum behavior.

This research may not only deepen our understanding of quantum physics, but may also push superconductor research in a completely new direction. The research results were published in the journal Nature Physics, titled “Unconventional superconducting quantum criticality in single-layer WTe2.”

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Lead assistant professor of physics Sanfeng Wu and his team found that when materials approach absolute zero, quantum mechanical fluctuations suddenly stop, exhibiting a series of unique quantum behaviors and properties that appear to be beyond the scope of existing theories.

“We directly observed quantum fluctuations near the transition and discovered a new quantum phase transition that does not fit the standard theoretical description known in the field. Once we understand this phenomenon, there is the possibility of an exciting new theory.”

The research began with a crystal of tungsten telluride (WTe2), a material classified as a layered semimetal. By peeling it back layer by layer, the researchers transformed it into a two-dimensional material just a single atomic layer thick. At this thinness, the material exhibits a range of novel quantum behaviors, such as being able to switch between insulating and superconducting phases.

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“You can transform a material from an insulator to a superconductor with just a tiny bit of gate voltage,” said Tiancheng Song, a postdoctoral researcher in physics and lead author of the paper. “It’s really an amazing effect.”

Can switch between insulating and superconducting phases

Vortex Nairn effect and electronic phase diagram of single layer WTe2. (Photo/”Nature Physics”)

One of the highlights of this research is the discovery of the existence of quantum vortices, which are like microscopic vortices that create tiny magnetic fields in materials. When the material is cooled to extremely low temperatures (minus 273.10 degrees Celsius), these vortices rapidly increase, eventually destroying the superconducting state and triggering a quantum phase transition.

A surprising discovery in the experiment is that when the electron density is adjusted below the critical value, these vortex signals suddenly disappear, as if they were “suddenly dead” by quantum fluctuations. This phenomenon surprised physicists because it might not be explained by existing theories.

“In other words, we have discovered a new type of quantum critical point, but we know nothing regarding it,” said N. Phuan Ong, a professor of physics at Princeton University.

In the field of condensed matter physics, there are currently two established theories that can explain the phase transition of superconductors, namely the Ginzburg-Landau theory and the BKT theory. However, the researchers found that none of these theories might explain the observed phenomena.

Wu added: “We need a new theory to describe this situation, which is something we hope to address in future theoretical and experimental work.”

This research not only opens up a new understanding of superconducting physics, but also challenges our knowledge of the quantum world, demonstrating that even the most fundamental principles in science can hold surprises and unsolved mysteries. It’s like finding an unknown secret passage in the microscopic world, which leads to a new and unknown quantum realm.

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Image Source:Nature Physicscc By4.0

Reference papers:

1.Unconventional superconducting quantum criticality in monolayer WTe2.Nature Physics

Further reading:

1.Quantum Energy Exchange: Exploring the Mysteries of Light Fields and Quantum Emitters

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