The possibility of implementing quantum spin liquids that will advance the next-generation quantum computing era has been confirmed for the first time in the world by our research team.

A joint research team led by Professor Chang-Hee Son of the Department of Physics at UNIST (President Jong-Rae Park) and Professor Heung-Sik Kim of the Department of Semiconductor Physics at Kangwon National University (President Jae-Yeon Jeong) succeeded in increasing quantum fluctuations in cobalt-based honeycomb-structured oxides. This is the first time in the world that the possibility of implementing quantum spin liquid has been confirmed.

In ordinary magnets, the spins of the electrons align when the temperature drops. It is similar to water turning into ice. However, quantum spin liquids remain liquid even at extremely low temperatures without the spins being aligned. This new state of matter could facilitate the development of ultra-fast quantum computers and innovative communication technologies.

The research team successfully controlled the deformation of the crystal structure by fabricating a cobalt-based honeycomb oxide as a thin film. By increasing the quantum fluctuation, the spin alignment temperature was reduced by more than half. It was proven that controlling the lattice distortion is the key variable that increases the quantum fluctuation.

Professor Philip Anderson, winner of the 1973 Nobel Prize in Physics, proposed the possibility of a quantum spin liquid, but it was not easy to implement. This is because most quantum spin candidates do not have strong quantum fluctuations, making it difficult to suppress spin alignment.

Professor Son Chang-hee explained, “This study has shown that a thin film structure can effectively control the spin interaction of a quantum spin liquid candidate material.” He added, “If a quantum spin liquid is implemented in a thin film form, it may be possible to implement a topological quantum computer that does not require quantum error correction.”

The results of this study were published online in Science Advances on July 5, 2024. The research was conducted with the support of the Ministry of Science and ICT, the National Research Foundation of Korea, and Pohang Accelerator Laboratory.