近日，美国加州大学的Stephen D.Wilson及其领导的研究小组取得一项新突破。他们发现了三角晶格磁体NaRuO₂的量子无序基态。相关研究成果已于2023年4月24日在国际知名学术期刊《自然—物理学》上发表。

该研究团队的发现表明，自旋–轨道耦合和相关效应在三角晶格磁体NaRuO₂中协同作用，产生了一种固有的涨落磁基态。尽管存在电荷间隙，研究人员发现在低温下自旋激发会在比热中产生类似于金属的项，并在中子散射中产生一系列激发，这与之前在三角晶格有机磁体中发现的自旋液体态类似。进一步冷却会产生一个不同的高度无序自旋态的交叉点，其动态自旋自相关函数反映了持续的涨落。这些发现将NaRuO₂定位为一种与有低温量子无序交叉点的有机海森堡自旋液体化合物相似的化合物。

据悉，长期以来，人们一直希望在实现三角晶格哈伯模型的材料中观察到自旋液体态。然而，弱自旋-轨道耦合和其他小扰动通常会导致常规自旋冻结或磁序。但是足够强的自旋-轨道耦合可以重整电子波函数并诱导各向异性交换相互作用，从而促进磁阻挫。

附：英文原文

Title: Quantum disordered ground state in the triangular-lattice magnet NaRuO₂

Author: Ortiz, Brenden R., Sarte, Paul M., Avidor, Alon Hendler, Hay, Aurland, Kenney, Eric, Kolesnikov, Alexander I., Pajerowski, Daniel M., Aczel, Adam A., Taddei, Keith M., Brown, Craig M., Wang, Chennan, Graf, Michael J., Seshadri, Ram, Balents, Leon, Wilson, Stephen D.

Issue&Volume: 2023-04-24

Abstract: It has long been hoped that spin liquid states might be observed in materials that realize the triangular-lattice Hubbard model. However, weak spin–orbit coupling and other small perturbations often induce conventional spin freezing or magnetic ordering. Sufficiently strong spin–orbit coupling, however, can renormalize the electronic wavefunction and induce anisotropic exchange interactions that promote magnetic frustration. Here we show that the cooperative interplay of spin–orbit coupling and correlation effects in the triangular-lattice magnet NaRuO₂ produces an inherently fluctuating magnetic ground state. Despite the presence of a charge gap, we find that low-temperature spin excitations generate a metal-like term in the specific heat and a continuum of excitations in neutron scattering, reminiscent of spin liquid states previously found in triangular-lattice organic magnets. Further cooling produces a crossover into a different, highly disordered spin state whose dynamic spin autocorrelation function reflects persistent fluctuations. These findings establish NaRuO₂ as a cousin to organic, Heisenberg spin liquid compounds with a low-temperature crossover in quantum disorder.

DOI: 10.1038/s41567-023-02039-x

Source: https://www.nature.com/articles/s41567-023-02039-x