A team of researchers affiliated with UNIST has succeeded in identifying traces of the Kitaev quantum spin liquid (QSL) using light. The Kitaev QSL represents a special quantum state that could pave the way for the development of error-free, large-scale quantum computers. However, experimentally confirmed instances of this phenomenon within materials have been scarce, prompting ongoing efforts to discover suitable candidate materials.
The new experimental methodology utilizing light for detecting the characteristics of Kitaev QSL is expected to aid in the exploration and characterization of quantum computing materials. The study is published in the journal Nature Communications.
The research team, led by Professor Changhee Sohn from the Department of Physics at UNIST, in collaboration with Professor Jae Hoon Kim’s team from Yonsei University and Professor Jung-Woo Yoo’s team from the Department of Materials Science and Engineering at UNIST, reported that they successfully detected the spin fluctuations indicative of the Kitaev QSL state in thin film cobalt-based oxides.
Kitaev QSL is a unique form of the quantum spin liquid state. In this state, spin particles within a solid do not align even at low temperatures, maintaining a fluid and disordered state akin to liquid molecules that exhibit dynamic fluctuations.
The collaborative team detected these spin fluctuations in cobalt-based oxides synthesized in a thin film format, measuring just 20 nm in thickness. While existing neutron-based analytical methods have made it easy to observe spin fluctuations in bulk materials, signals become weak and challenging to observe when materials are reduced to thin film formats, which is essential for quantum computing applications.
The researchers utilized an innovative approach, analyzing exciton particles generated by illuminating the thin film with light, to detect these spin fluctuations. Notably, the measured spin fluctuations persisted above a specific temperature known as the Néel temperature (16K, -257.15°C), providing evidence that these fluctuations arise not merely due to thermal effects but are a characteristic of the quantum spin liquid state. Additionally, theoretical calculations confirmed strong Kitaev interactions, typically found in Kitaev QSLs rather than standard quantum spin liquids.
Professor Sohn stated, “This research demonstrates that the characteristics of Kitaev QSL can manifest in cobalt-based oxides in thin film form. Moreover, our analytical method used in the experiment is expected to contribute significantly to the development of quantum computing materials.”
More information:
Baekjune Kang et al, Optical detection of bond-dependent and frustrated spin in the two-dimensional cobalt-based honeycomb antiferromagnet Cu3Co2SbO6, Nature Communications (2025). DOI: 10.1038/s41467-025-56652-w
Provided by
Ulsan National Institute of Science and Technology
Citation:
Light reveals unique quantum spin liquid state, promising error-free computing (2025, March 19)
