A magnetic layer sandwiched by non-magnetic layers containing a mixture of right- and left-handed enantiomers shows properties of a quantum state known as a spin liquid

We found that quantum-like magnetic behavior characteristic of a spin liquid can emerge in a magnetic layer when it is sandwiched by non-magnetic layers containing a mixture of right- and left-handed (enantiomeric) molecules. This result suggests a new materials-design route for stabilizing quantum fluctuations and may aid both future quantum technologies and fundamental studies of electron behavior.

Some molecules come in two mirror-image forms, often described as “right-handed” and “left-handed.” Such pairs are called enantiomers. Although they look almost identical, they can behave very differently—for example, in some medicines, only one of the two forms is effective. In recent years, researchers in functional materials have also actively explored making molecules and metal complexes in right-handed or left-handed forms in order to tune properties such as magnetism and electrical conduction.

In this study, we targeted a special magnetic state known as a quantum spin liquid. In ordinary magnets, tiny magnetic moments (spins) align into an ordered pattern at low temperature. In a quantum spin liquid, however, spins do not settle into a fixed order even at extremely low temperatures, and quantum fluctuations remain. This state has attracted attention for about half a century, and realizing and understanding it is still a major challenge.

For molecular-crystal magnets, a widely used guideline has been that strong quantum fluctuations are favored when the valence electrons—which carry the spins—sit at the vertices of an equilateral triangular lattice. Many studies have therefore focused on how to design the “lattice” of the magnetic molecular layer, and also on what happens when enantiomers are introduced directly into the magnetic layer itself.

Here we took a different approach. Rather than making the magnetic layer right-handed or left-handed, we examined what happens when the non-magnetic layers that sandwich the magnetic layer are built from enantiomeric ions. The key point is that these non-magnetic layers contain a mixture of right-handed and left-handed ions, instead of being composed of only one form.

We synthesized a new layered molecular crystal, κ-(BEDT-TTF)₂[B_R/S(salicylate)₂], and determined its structure in detail. In this material, the magnetic layer is sandwiched by non-magnetic layers that include both right-handed and left-handed ions.

We then evaluated its properties using multiple complementary methods, including electrical resistivity, magnetization, specific heat, spectroscopy, and calculations. These measurements revealed low-temperature behaviors consistent with enhanced quantum fluctuations and suggestive of a spin-liquid–like quantum state.

Importantly, the magnetic layer in this compound is not close to an equilateral triangular arrangement—in other words, it is not an ideal condition for realizing a spin liquid by the usual guideline. Even so, signatures of strong quantum fluctuations emerge when the magnetic layer is sandwiched by non-magnetic layers containing a mixed set of right-handed and left-handed enantiomeric ions.

These results show a new pathway for materials design: using enantiomers not on the magnetism-carrying side, but in the sandwiching non-magnetic layers, and keeping the right-handed and left-handed forms mixed rather than selecting only one. This approach may provide a useful hint for exploring materials relevant to future quantum technologies such as quantum computing. At the same time, by making quantum behavior easier to observe and analyze, it may also advance fundamental research aimed at revealing the intrinsic properties of electrons in solids.

Bibliographic Information

Title:2D Quantum Spin-Liquid Candidate Including a Chiral Anion: κ-(BEDT-TTF)₂[B_R/S(salicylate)₂]
Authors:T. J. Blundell, K. Sneade, J. O. Ogar, S. Yamashita, H. Akutsu, Y. Nakazawa, T. Yamamoto, and L. Martin,
Journal:Journal of the American Chemical Society, 147(7), (2025) 5658-5668
Feb 6, 2025
DOI:10.1021/jacs.4c12386

Fundings

• JSPS KAKENHI 23K04691

Media

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  Schematic illustration of the molecular arrangement in the layered molecular magnet κ-(BEDT-TTF)₂[B_R/S(salicylate)₂]

  credit : Takashi Yamamoto
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