Scientists Discovered a New, Deeply Weird Quantum State

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Here’s what you’ll learn when you read this story:

• A computer model helped isolate a “pinball state” where matter switches back and forth between states.

• Scientists studied a specific setup of quantum materials in order to see what may be possible.

• Electrons that switch from moving (conducting) to sticking (insulating) would be highly prized.

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Scientists from Florida State University are highlighting a weird state of matter in research that appears now in the peer reviewed journal Nature Partner Journals Quantum Materials. As it turns out, under the right conditions, carefully patterned electrons enter what the researchers are calling a “pinball state,” where their charge attraction switches on and off. The team was able to achieve this state by creating a very specific version of what’s known as a Wigner crystal—a substance made entirely and exclusively of densely packed electrons—using a super high-tech “stencil.”

This “stencil” took the form of a specially prepared surface called moiré. In daily life, we see moiré patterns regularly—if you’ve seen a striped shirt appear to “vibrate” on TV, that’s one example of moiré. In science, the idea of moiré is fundamentally pretty similar, but instead of those trippy-looking patterns being artifacts of video resolution, they are the results of layers of incredibly thin, carefully patterned films being stacked on top of each other and slightly offset.

And ‘incredibly thin’ is no overstatement—more and more, scientists engineer nanomaterials that are just one molecule, atom, or particle thick. The thickness itself isn’t new—electroplating dates back to 1805, and produces layers that qualify as technical “thin films” that are mere micrometers thick. But these films can still take on novel forms, being designed with patterns or shaped into carbon nanotubes, for example.

When the “stencil” (made of two layers of moiré film) was placed on a material called a substrate, and electrons were introduced into the system, those electrons organized themselves in accordance with the “stencil” into a Wigner crystal. And from there, the scientists were able to tweak variables like density and temperature to create something never seen before.

“In our study, we determined which ‘quantum knobs’ to turn to trigger this phase transition and achieve a generalized Wigner crystal,” Hitesh J. Changlani, a coauthor of the study, said in a Florida State statement, “which uses a 2D moiré system and allows different crystalline shapes to form, like stripes or honeycomb crystals, unlike traditional Wigner crystals that only show a triangular lattice crystal.”

In other words, the ‘typical’ triangular Wigner crystal seen in a two-layer system can be twisted and tuned until its potential, and the potential energy in its system, is maximized. And under the right, weird conditions (and in the right, weird shapes), the system can “bounce” between states of matter like a pinball. This behavior was previously theorized, the researchers explain, but their more-realized computer model shows that the pinball state is plausible in real life… but maybe only inside a near-absolute-zero freezer.

“Our work addresses currently unresolved aspects of these experiments, contributing to the theoretical understanding of the moiré TMD [twisted metal dichalcogenide] systems and presenting both zero-temperature and finite-temperature studies in a unified framework,” the team wrote. “[One] objective,” they continued, “is to understand the finite temperature melting of these [generalized Wigner crystals (GWCs)],” and another was to probe the stability of the layered model that fosters the GWCs.

The “partially melted” or “pinball liquid” phase, they found, is unexpectedly stable (though, with quantum states at near absolute zero temperatures, stability is relative). In this phase, some electrons “want to freeze and others want to float around, which means that some are insulating and some are conducting electricity,” Cyprian Lewandowski, one of the authors of this study, said in a press release. “This is the first time this unique quantum mechanical effect has been observed and reported for the electron density we studied in our work.”

And while it’s less glamorous than the pinball state, in this paper, the researchers also found some ways that physicists studying GWCs can liken parts of their systems to other models in order to clarify their work. These imperfect or partial analogies could help shake loose further insights and paths of inquiry and are essential to science.

The team behind this work knows that this line of research is far from over.“[W]hen you think of turning a liquid into gas, you picture turning up a heat knob to get water to boil into steam,” Lewandowski said in the statement. “Here, it turns out there are other quantum knobs we can play with to manipulate states of matter, which can lead to impressive advances in experimental research.”

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