Researchers have recently found evidence of “dark electrons” in solid-state materials, electrons that cannot be detected even using spectroscopy.
After analyzing the electrons in palladium diselenide (PdSe₂), the team discovered certain states that cancel each other’s functions, rendering these “dark states” of electrons unobservable.
Scientists believe that this phenomenon is likely present in many other substances, which can help us understand why certain superconductors exhibit unexpected behaviors.
When you shine a flashlight beam onto a blank wall, you might unexpectedly see a series of light rings forming at the collision point. This is due to the interference effect – when light waves collide in sync in tight or loose patterns. When waves sync up, constructive interference occurs, making the signal brighter. Conversely, if the waves do not align, destructive interference happens, dimming the signal. When waves are completely opposite, the most extreme destructive interference occurs, with no signal at all.
Light is the most common example, but not the only phenomenon that can cause interference. Interestingly, when electrons have completely different energy levels, they also exhibit interference, which may lead to the generation of “dark electrons” – electrons in “dark states” that cannot be observed through a spectrometer.
For a long time, people believed these mysterious electrons do not exist in solid-state materials. Since electrons cannot be too far apart, it was thought they cannot have completely different energy levels. However, a recent study led by South Korean researchers found that these states can occur even in condensed matter. This discovery could have profound implications for our understanding of quantum physics. The research paper was published in the journal “Nature Physics” on July 29.
“This hidden state may be the crucial missing piece of information for understanding elusive quantum phenomena,” the authors pointed out in their research report. “Therefore, identifying other unknown dark states in nature and uncovering the mechanisms behind them is crucial.”
The research team initially searched for these dark states in a crystalline material called palladium diselenide (PdSe₂). They studied the behavior of electrons in this material and found certain energy bands where electrons were expected to exist but were essentially invisible. To confirm that the observed dark states were caused by the electrons themselves and not by the detection light source, they conducted various light polarization tests on the material.
Once they identified these energy bands, the researchers used models to extend this discovery to other systems. Excitingly, they were able to relatively easily (at least in the field of quantum mechanics) generalize these results. Their study indicates that the dark electrons found in PdSe₂ are not just random phenomena – they suggest that dark states are likely prevalent in the natural world.
As one of the co-authors of the study, Keun Su Kim, highlighted in an interview with “New Scientist” magazine, this discovery could help explain why some materials exhibit superconducting properties under unexpected conditions. If we cannot even see their partial quantum behavior, it’s not surprising that we were confused before. However, now that we know what to look for, this may bring some much-needed theoretical explanations in physics.
In the field of science, darkness often symbolizes mysteries. However, sometimes the mystery itself is the answer – at least until we delve deeper into exploration. ◇