(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)
- KAIST-Yonsei university researchers developed innovative dipole technology to maximize near-infrared photon harvesting efficiency - Overcoming the shortcoming of existing perovskite solar cells that cannot utilize approximately 52% of total solar energy - Development of next-generation solar cell technology with high efficiency and high stability that can absorb near-infrared light beyond the existing visible light range with a perovskite-dipole-organic semiconductor hybrid structure &l
2024-10-31- Professor Yong-Hoon Kim's team from the School of Electrical Engineering succeeded in accelerating calculations for electronic structure in quantum mechanics for the first time in the world using a convolutional neural network (CNN) model - Presenting the learning principle of quantum mechanical 3D chemical bonding information through AI, expected to be applied to next-generation material and device computer design fields The close relationship between AI and highly complicated scientific
2024-10-30- A KAIST research team led by Professor Keon Jae Lee has developed a deep skin-stimulating LED mask which has been verified in clinical trials to improve dermis elasticity by 340%. < Figure 1. Overall concept of face-fit surface-lighting micro-LEDs (FSLED) mask. a. Optical image of the FSLED mask showing uniform surface-lighting. schematic illustration of the FSLED mask. The 2D to 3D transformation procedure b. Difference in cosmetic effect on deep skin elasticity, wrinkles, and sagging
2024-10-29< Group photo of our research team participating in the 3rd Cybathlon > The Cybathlon is an international competition, which aims to help overcome disabilities through the use of robotics technology. KAIST researchers came in third, winning the bronze medal, at their 1st participation in 2016, won their first gold medal at the 2nd competition in 2020, and took back the gold medal at this year’s 3rd competition, successfully defending their champion title. KAIST (President Kwa
2024-10-28< Photo. Professor Uichin Lee (left) receiving the award > KAIST (President Kwang Hyung Lee) announced on the 25th of October that Professor Uichin Lee’s research team from the School of Computing received the Distinguished Paper Award at the International Joint Conference on Pervasive and Ubiquitous Computing and International Symposium on Wearable Computing (Ubicomp / ISWC) hosted by the Association for Computing Machinery (ACM) in Melbourne, Australia on October 8. The ACM
2024-10-25