(Professor Han (far right) and his research team)
A KAIST research team observed a new quantum mechanical magnetic state ‘Jeff = 3/2.’ This first observation of ‘Jeff=3/2’ could be the foundation for future research on superconductivity and quantum magnetism.
In quantum mechanics, total angular momentum is defined as the sum of spin and orbital angular momenta and is denoted with the ‘J.’ The newly identified magnetic moment can be described as a kind of angular momentum that occurs when specific conditions are met and has been denoted ‘Jeff’ with the meaning ‘effective angular momentum’ in the field. Jeff=3/2 has been a topic of discussion but was yet to be observed.
The research was co-led by Professor Myung Joon Han of the Department of Physics at Chung-Ang University in Korea, RIKEN in Japan, and the Argonne National Laboratory in the US. This research was published in Nature Communications on October 14, 2017.
In academia, spin-orbital coupling was known to lead to a unique quantum state and has been an active area of recent research. In contrast to magnetic moment by electron spin and orbital, the effective magnetic moment Jeff, formed from the coupling of the two, shows a unique ground state and interaction patterns, which could lead to new phenomena and properties.
Most studies in the last decade focused on ‘Jeff=1/2’, but there has not been any observation of ‘Jeff=3/2’, which led to slow progress. In 2014, the research team led by Prof. Han theoretically predicted the possibility of the ‘Jeff=3/2’ state in a certain type of materials based on molecular orbital, instead of atomic orbital. In the current study, the team applied the Selection Rule of quantum mechanics for the ‘Jeff=3/2’ state, which differs to the general spin moment, in order to experimentally detect this moment.
When electrons near the atomic nucleus are excited by X-rays, the excited electrons can be absorbed or re-emitted through interactions with other electrons. Here, the Selection Rule is applied to electrons. According to quantum mechanics, this rule is very unique in the ‘Jeff=3/2’ state and ‘Jeff=3/2’ is predicted to be distinguishable from general spin states. The prediction that was made using this idea was verified through the experiment using electrons extracted from tantalum at two different energy levels. In this material, the unique quantum mechanical interference by the ‘Jeff=3/2’ moment can be taken as direct evidence for its existence.
The new quantum state is very unique from any of the previously known magnetic states and this study could be the starting point for future research on the ‘Jeff=3/2’ moment. Further, this finding could contribute to future research on various properties of the magnetic states and its interactions.
(Figure 1: Crystal structure, MO levels, and RIXS process in GaTa4Se8.)
(Figure 2: Cluster model calculations of the L3 and L2 RIXS spectra)
Professor Seok-Hyung Bae’s research team at the Department of Industrial Design developed a novel 3D sketching system that rapidly creates animated 3D concepts through simple user interactions like sketching on a piece of paper or playing a toy. Foldable drones, transforming vehicles, and multi-legged robots from sci-fi movies are now becoming commonplace thanks to technological progress. However, designing them remains a difficult challenge even for skilled experts, because complex de2022-11-23
A KAIST research team led by Ph.d candidate Jae Hee Lee and Professor Keon Jae Lee from the Department of Materials Science and Engineering has developed a surface-lighting microLED patch for UV-induced melanogenesis inhibition. Melanin is brown or dark pigments existing in the skin, which can be abnormally synthesized by external UV or stress. Since the excessive melanin leads to skin diseases such as spots and freckles, proper treatment is required to return normal skin condition. Rece2022-11-22
< Professor Youjip Won of KAIST School of Electrical Engineering > Professor Youjip Won of KAIST School of Electrical Engineering was elected as the President of Korean Institute of Information Scientists and Engineers (KIISE) for the Succeding Term for 2023 on November 4th, 2022. Professor Won will serve as the 39th President of KIISE for one year starting from Jan. 1, 2024. He is one of the leading experts on Operating Systems, with a particular emphasis on storage systems. Ko2022-11-15
[ From left, Ph.D. candidates See-On Park and Hakcheon Jeong, along with Master's student Jong-Yong Park and Professor Shinhyun Choi ] See-On Park, Hakcheon Jeong, Jong-Yong Park - a team of researchers under the leadership of Professor Shinhyun Choi of the School of Electrical Engineering, developed a highly reliable variable resistor (memristor) array that simulates the behavior of neurons using a metal oxide layer with an oxygen concentration gradient, and published their work in Nature2022-11-01
KAIST (President Kwang Hyung Lee) held the 'KAIST-NYU Digital Governance Forum' at the Korea Press Center in the morning of October 28th, 2022. This forum was held in continuation to discuss the objectives of the 'Digital Vision Forum' that was hosted by New York University (NYU) back in September in the United States, and is the first public event to be held through joint efforts by KAIST and NYU since the signage of the 'KAIST-NYU Joint Campus' was presented at the New York forum.2022-10-28