Breakthrough in the study of frustrated ferro-antiferromagnets: Rb₂Cu₂Mo₃O₁₂ and Cs₂Cu₂Mo₃O₁₂

Linear-chain molybdates A₂Cu₂Mo₃O₁₂ (A = Rb, Cs) are among the most intriguing frustrated quasi-one-dimensional quantum ferro-antiferromagnets [1]. For over a decade extensive experimental and theoretical work focused on the unique magnetoelectric effect in Rb₂Cu₂Mo₃O₁₂ [2,3], and on spin-nematic Tomonaga-Luttinger liquid behavior in Cs₂Cu₂Mo₃O₁₂ [4]. Unfortunately, a lack of single-crystal samples has hampered any further progress. In a breakthrough, our group has succeeded in growing single crystals for both materials. Subsequent measurements revealed that their magnetic properties are even more complex and intriguing than originally thought [5-7]. The previously reported chiral-spin-liquid and magnetoelectric high-temperature phase in Rb₂Cu₂Mo₃O₁₂ [3] was shown to be spurious and due to impurities. Our comprehensive thermodynamic study mapped out the highly anisotropic low-temperature phase diagram with quantum critical points of different effective dimensionalities [5]. Dielectric experiments revealed this material to be a quantum multiferroic and enabled the first direct excitation-response measurements of critical susceptibility at a magnetic BEC quantum critical point [6]. For the Cs system, a host of exotic field-induced phases was discovered, including a robust presaturation phase that is likely to be a spin-nematic phase [7]. New results pertain to its unconventional magnetoelectric response.

 

References

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[2] Y. Yasui et al., J. Appl. Phys. 113, 17D910 (2013).

[3] H. Ueda et al., Phys. Rev B 101, 140408(R) (2020).

[3] Y. Hoshino et al., JPS Conf. Proc. 3, 014012 (2014).

[4] S. Hayashida et al., Phys. Rev. B 100, 134427 (2019).

[5] S. Hayashida et al., Phys. Rev. Research 3, 033053 (2021).

[6] D. Flavián et al., Phys. Rev. B 101, 22408 (2020).