Quantum Breakthrough: Unveiling the Mysteries of Electron Tunneling

Tunneling is a fundamental process in quantum mechanics, involving the ability of a wave packet to cross an energy barrier that would be impossible to overcome by classical means. At the atomic level, this tunneling phenomenon significantly influences molecular biology. It aids in speeding up enzyme reactions, causes spontaneous DNADNA, or deoxyribonucleic acid, is a molecule composed of two long strands of nucleotides that coil around each other to form a double helix. It is the hereditary material in humans and almost all other organisms that carries genetic instructions for development, functioning, growth, and reproduction. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>DNA mutations, and initiates the sequences of events that lead to the sense of smell.

Photoelectron tunneling is a key process in light-induced chemical reactions, charge and energy transfer, and radiation emission. The size of optoelectronic chips and other devices has been close to the sub-nanometer atomic scale, and the quantum tunneling effects between different channels would be significantly enhanced.

The electronic chip and the Van der Waals complex with an internuclear distance 0.39 nm. Credit: Ming Zhu, Jihong Tong, Xiwang Liu, Weifeng Yang, Xiaochun Gong, Wenyu Jiang, Peifen Lu, Hui Li, Xiaohong Song & Jian Wu

The real-time imaging of electron tunneling dynamics in complex has important scientific significance for promoting the development of tunneling transistors and ultrafast optoelectronic devices. The effect of neighboring atoms on electron tunneling dynamics in the complex is one of the key scientific issues in the fields of quantum physics, quantum chemistry, nanoelectronics, etc.

Recent Research Developments

In a new paper published in Light Science & Application, a team of scientists from Hainan University and East China Normal University designed a van der Waals complex Ar-Kr⁺ as a prototype system with an internuclear distance of 0.39 nm to track the electron tunneling via the neighboring atomAn atom is the smallest component of an element. It is made up of protons and neutrons within the nucleus, and electrons circling the nucleus.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>atom in the system of sub-nanometer scale.

The electron emitted from Ar atom is firstly trapped to the highly excited transient states of the Ar-Kr+* before its eventual release to the continuum. A linearly polarized pump laser pulse is used to prepare the Ar-Kr+ ion by removing e1 from Kr site, and a time-delayed elliptically polarized probe laser pulse is used to track the electron transfer mediated electron tunneling dynamics (e2, orange arrow). Credit: Ming Zhu, Jihong Tong, Xiwang Liu, Weifeng Yang, Xiaochun Gong, Wenyu Jiang, Peifen Lu, Hui Li, Xiaohong Song & Jian Wu

The intrinsic electron localization of the highest occupied molecular orbital of Ar-Kr gives a preference for electron removal from the Kr site in the first ionization step. The site-assisted electron-hole in Ar-Kr⁺ guarantees that the second electron is mainly removed from the Ar atom in the second ionization step, where the electron may straightly tunnel to the continuum from the Ar atom or alternatively via the neighboring Kr⁺ ionic core.

In combination with the improved Coulomb-corrected strong-field approximation (ICCSFA) method developed by the team, which is able to take into account the Coulomb interaction under the potential during tunneling, and by monitoring the photoelectron transverse momentum distribution to track the tunneling dynamics, then, it was discovered that there are two effects of strong capture and weak capture of tunneling electrons by a neighboring atom.

This work successfully reveals the critical role of neighboring atoms in electron tunneling in sub-nanometer complex systems. This discovery provides a new way to deeply understand the key role of the Coulomb effect under the potential barrier in the electron tunneling dynamics, solid high harmonics generation, and lays a solid research foundation for probing and controlling the tunneling dynamics of complex biomolecules.

Reference: “Tunnelling of electrons via the neighboring atom” by Ming Zhu, Jihong Tong, Xiwang Liu, Weifeng Yang, Xiaochun Gong, Wenyu Jiang, Peifen Lu, Hui Li, Xiaohong Song and Jian Wu, 16 January 2024, Light: Science & Applications.
DOI: 10.1038/s41377-023-01373-2

The study was funded by the National Natural Science Foundation of China, the Hainan Provincial Natural Science Foundation of China, Fundamental Research Funds for the Central Universities, and the Sino-German Center for Research Promotion.