Professor Shim Heung-seon of KAIST Awarded July Science and Technology Person of the Month

World's First Demonstration of Spin Cloud Determining Magnetism of Impurities in Metals and Semiconductors

[Asia Economy Reporter Kim Bong-su] The Ministry of Science and ICT and the National Research Foundation of Korea announced on the 30th that Professor Shim Heung-seon (photo) of the Department of Physics at the Korea Advanced Institute of Science and Technology (KAIST) has been selected as the recipient of the "Scientist of the Month" award for July.

Professor Shim was the first in the world to prove the existence of the spin cloud that masks the magnetism of impurities in metals and semiconductors. The Kondo effect, in which the spin of impurities in conductors or semiconductors is masked by a spin cloud generated by surrounding free electrons, was first discovered in the 1930s. Over the past 50 years, many research teams have attempted theoretical elucidation and experimental verification, but all failed to observe the spin cloud, leading to debates about its existence.

In 2013, Professor Shim predicted that applying an electric field inside and outside the Kondo spin cloud would generate different currents, and proposed a method to observe the Kondo spin cloud using this principle. A joint research team from Japan's RIKEN developed a semiconductor quantum device capable of applying electric fields at various locations around the impurity spin based on Professor Shim's theoretical proposal. Professor Shim's team then analyzed the electrical signals of the device observed at extremely low temperatures (-273.05℃) to confirm the size and spatial distribution of the spin cloud, thereby proving for the first time the existence of a micrometer (10^-6 meter) scale spin cloud.

The research results were published in the international journal Nature in March 2020. Professor Shim stated, “This study is significant in proving the existence of the spin cloud, which had been controversial, and in generating and confirming a micrometer-sized spin cloud using semiconductor quantum devices,” adding, “I hope the research results will lead to the development of future semiconductor technologies.”

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