New Crystal Superconductor PtBi₂ Stuns Scientists With Never-Seen-Before Behavior

Researchers have found something remarkable in a simple-looking crystal called PtBi₂. At first glance, the material appears ordinary. However, new findings show that its electrons behave in a completely unexpected way.Scientists at IFW Dresden and the ct.qmat research cluster made this discovery. In earlier work, they learned that the top and bottom surfaces of PtBi₂ become superconducting. This means electrons pair up and flow without resistance. Now, they report that this pairing follows rules that no other known superconductor shows.

Strange Surface Behavior

The team breaks PtBi₂’s behavior into three clear steps.
First, certain electrons stay only on the top and bottom surfaces. This happens because of the material’s stable topological structure. These features remain even when the crystal changes shape or thickness.In addition, each surface always has a matching electronic partner on the opposite side. If the material is cut, both new surfaces instantly form their own surface-bound electrons.Second, only the surface electrons pair up at low temperatures. The inner electrons behave like they do in regular metals. As a result, the crystal becomes a natural “superconducting sandwich” with a normal middle.

A Six-Direction Mystery

Finally, new high-resolution measurements reveal something even stranger. Electrons traveling in six specific directions refuse to pair up. This reflects a unique six-fold symmetry in the material. Other superconductors may show four-fold symmetry, but none have shown six.
“We have never seen this before,” says Dr. Sergey Borisenko.

Majorana Particles on the Edges

The study also confirms that PtBi₂ naturally hosts Majorana particles along its edges. These particles could help create more stable quantum bits in future quantum computers.Researchers now aim to control these particles. For example, thinning the crystal or applying magnetic fields could shift how these particles behave.