Researchers discover new quantum material through ‘spin cloud’ condensation

2023. 2. 7. 12:24
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Professor Im Hyunsik at Dongguk University at a press conference that took place on Monday [Photo by Yonhap]
A group of physicists have demonstrated for the first time that a new quantum material can be formed when “spin clouds” are condensed at extremely low temperature.

A joint research team led by Professor Im Hyunsik at Dongguk University discovered the “spin clouds” condensation in a silicon metal at extremely low temperature, which is similar to a “Bose–Einstein condensate,” said the Ministry of Science and ICT on Tuesday.

A “spin cloud” refers to a phenomenon where internal impurities create magnetic forces when embedded in a metal and at extremely low temperatures, and itinerant electrons overlap with each other and form a “cloud.”

They are known to play an important role in high-temperature superconductivity that can be used for maglev levitation trains and magnetic resonance imaging. However, the phenomenon was not demonstrated until 2020, some 70 years after its first discovery in the 1930s, as there was a range of challenges in creating an environment in which one could conduct the experiments, including the extremely low temperature.

Research was based on the phenomenon that gas particles become liquid at lower temperatures. They created an environment at temperatures near absolute zero or minus 273.15 degrees Celsius, where spin clouds condense, and then they examined the elements that formed in that environment, which was “analogous to a Bose–Einstein condensate.” The research team was able to detect it by performing spectroscopy and electrical conductivity measurements.

Professor Im explaining a Bose–Einstein condensate [Photo by Yonhap]
A Bose–Einstein condensate is a state where boson particles condense at extremely low temperatures and appear to look like a single particle with a quantum element. This is also dubbed as the “fifth state of matter,” different from solids, liquids, gases or plasma.

“A boson is a particle whose spin quantum number has an integer value. Spin clouds can be seen as a particle whose spin quantum number is zero, as their magnetic forces are offset, and it is for this reason that it can be compared to a Bose-Einstein condensate,” the research team explained.

The researchers were able to demonstrate the phenomenon after seven years of study. In 2015, the physicists found a new, unconventional signal in a silicon metal as they were pursuing a study concerning quantum computer devices.

The scientists expect their latest research to help better understand spin interactions in metals and semiconductors, as well as high-temperature superconductors.

The research team will further expand its research into spin clouds to cover pure metals, in order to learn more about the characteristics of spin clouds.

“Changes in electrical conductivity at extremely low temperatures imply that this can be used as sensors for temperatures or magnetic fields in certain sectors,” said Professor Im during a press conference that took place on Monday. “As one spin cloud itself is fairly independent by quantum entanglement, it may be able to be used for quantum bits in quantum computers when applicable.”

The research was jointly conducted by Professors Kim Eun Kyu and Sin Sang-in from Hanyang University and Professor Chong Yonuk from Sungkyunkwan University, and published in Nature Physics, one of the most renowned international academic journals in physics.

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