In a groundbreaking study published in Physical Review Letters, researchers led by Professor Dong Eon Kim of POSTECH’s Department of Physics have solved a century-old mystery surrounding quantum tunneling. This study, conducted in collaboration with the Max Planck Institute for Nuclear Physics, sheds light on the surprising behavior of electrons within a quantum tunnel. For the first time, scientists have witnessed the complex interactions occurring inside the tunnel, revealing a hidden collision process that challenges long-held beliefs about the nature of quantum mechanics. The results of this study are poised to reshape the understanding of electron dynamics and fuel advances in technologies such as quantum computing, semiconductors, and ultrafast lasers.
Quantum Tunneling: The Mysterious Passage of Electrons
Quantum tunneling is a phenomenon that has fascinated physicists for decades. It allows particles like electrons to pass through energy barriers that they seemingly don’t have enough energy to overcome. Think of it as an invisible path cutting through a seemingly impenetrable wall. While the concept sounds like science fiction, quantum tunneling is critical in many physical processes, such as the functioning of semiconductors in modern electronics and nuclear fusion in the sun.
However, until now, what actually happens inside the tunnel, during the process of tunneling itself, has remained largely unknown. While scientists were able to observe the entry and exit of electrons from these quantum barriers, the intricate dynamics within the barrier have never been fully captured. This study marks a crucial milestone, not just in answering this longstanding question, but in the potential for new technologies that rely on precise control of electron behaviors.
The Breakthrough: Revealing the Hidden Collision
For the first time in history, scientists have directly observed what occurs inside the quantum tunnel. This is a critical development that could change the course of research into quantum mechanics. The research team, led by Professor Kim Dong Eon and Professor C.H. Keitel at the Max Planck Institute, employed intense laser pulses to induce electron tunneling in atoms. Using this technique, they observed a surprising phenomenon: rather than merely passing through the barrier, the electrons were found to collide with the atomic nucleus while still within the tunnel.
This unexpected discovery is termed under-the-barrier recollision (UBR), and it fundamentally alters our understanding of the tunneling process. Previously, scientists believed that electrons could only interact with the nucleus after exiting the tunnel. This new finding suggests that such interactions can indeed take place within the barrier, opening up an entirely new layer of complexity in how we understand tunneling.
A New Form of Energy Transfer Inside the Tunnel
What makes this discovery even more intriguing is the mechanism through which electrons gain energy during their tunneling journey. The team observed that the electrons not only passed through the barrier but also experienced a gain in energy inside the tunnel. This energy transfer is tied to a phenomenon known as Freeman resonance—an ionization process that was found to be significantly more intense than previously known ionization mechanisms. Interestingly, the ionization remained consistent regardless of changes in laser intensity, suggesting a deeply fundamental interaction at play inside the barrier.
This under-the-barrier recollision challenges traditional models of tunneling, which expected minimal or no interaction between electrons and atomic nuclei during the tunneling phase. The observation that the electrons actually collide with the nucleus, gain energy, and contribute to greater ionization could have profound implications for the development of quantum technologies, including more efficient lasers and better semiconductors.
A Step Forward in Quantum Control
The implications of this discovery go beyond basic science. As Professor Kim Dong Eon mentioned, “Through this study, we were able to find clues about how electrons behave when they pass through the atomic wall.” He added, “Now, we can finally understand tunneling more deeply and control it as we wish.” The ability to control electron dynamics with such precision could have a revolutionary impact on fields that depend on tunneling processes, such as quantum computing, semiconductor design, and ultrafast lasers.
For example, the understanding of how electrons interact inside quantum barriers could allow for the creation of new materials that exhibit more efficient electron movement, leading to faster and more powerful computing systems. Similarly, the ability to control tunneling could enable more precise manipulation of semiconductor components, paving the way for the next generation of electronic devices.