Science solved century old mystery that lies inside every AMD, Intel, Nvidia CPU, GPU

Scientists finally understand more about electron tunneling, a phenomenon that allows electrons to pass through energy barriers.

A team of physicists led by Professor Dong Eon Kim from POSTECH, working with colleagues at the Max Planck Institute in Germany, has made a breakthrough in understanding one of quantum mechanics’ most puzzling ideas that has been around for over a century: electron tunneling. Their study, published in Physical Review Letters, shows for the first time what actually happens when electrons move through barriers that should normally block them.

Electron tunneling which is kind of quantum tunneling is a strange but very real effect where particles like electrons pass through energy barriers that they shouldn’t be able to cross according to classical physics. This process is at the heart of how semiconductors work, which power smartphones and computers, and it also plays a role in nuclear fusion, the reaction that fuels the sun. Until now, scientists only knew what happens before and after tunneling, but the details of what occurs inside the barrier remained unknown.

To investigate, the team used powerful laser pulses to push electrons into tunneling. What they found was surprising. Instead of simply slipping through, electrons actually collide again with the atomic nucleus while still inside the barrier. The researchers named this process “under-the-barrier recollision” (UBR). This discovery challenges the long-standing belief that electrons only interact with the nucleus after leaving the tunnel.

The study focused on what is called nonadiabatic tunneling in strong-field ionization, tested across a wide range of laser intensities. The UBR model goes beyond the older idea of direct multiphoton transitions, which could not explain certain features of tunneling. The new model predicted two key outcomes: first, that high-order Freeman resonances (FR) would dominate over above-threshold ionization in the photoelectron energy spectra, and second, that the FR signal would remain flat regardless of changes in laser intensity.

Experiments confirmed both predictions. Electrons were seen to gain energy inside the barrier and then collide again with the nucleus, which strengthened Freeman resonance. This led to ionization levels much higher than those seen in earlier processes and showed little sensitivity to laser intensity. These results matched the UBR model and gave scientists a clearer picture of tunneling dynamics.

Professor Kim explained the importance of the work, saying, “Through this study, we were able to find clues about how electrons behave when they pass through the atomic wall,” and added, “Now, we can finally understand tunneling more deeply and control it as we wish.”

This research not only solves a century-old mystery but also opens the door to practical advances. A better grasp of tunneling could help improve technologies that depend on it, such as semiconductors, quantum computers, and ultrafast lasers. For technology enthusiasts, the takeaway is simple: understanding how electrons behave in tunneling could lead to faster, more efficient devices and new possibilities in physics that were once thought impossible.

Source: POSTECH, APS Journals

This article was generated with some help from AI and reviewed by an editor. Under Section 107 of the Copyright Act 1976, this material is used for the purpose of news reporting. Fair use is a use permitted by copyright statute that might otherwise be infringing.

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Posted Tuesday 7 April 2026 at 1:06 pm AEST (my time).

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