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arXiv 2402.15869cond-mat.str-el
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量子伊辛磁体 K$_2$Co(SeO$_3$)$_2$ 中超固体的相图与光谱学特征

Phase Diagram and Spectroscopic Signatures of a Supersolid in Quantum Ising Magnet K$_2$Co(SeO$_3$)$_2$

Tong Chen, Alireza Ghasemi, Junyi Zhang, Liyu Shi, Zhenisbek Tagay, Youzhe Chen, Lei Chen, Eun-Sang Choi, Marcelo Jaime, Minseong Lee, Yiqing Hao, Huibo Cao, Ba… 展开作者

Tong Chen, Alireza Ghasemi, Junyi Zhang, Liyu Shi, Zhenisbek Tagay, Youzhe Chen, Lei Chen, Eun-Sang Choi, Marcelo Jaime, Minseong Lee, Yiqing Hao, Huibo Cao, Barry Winn, Andrey A. Podlesnyak, Daniel M. Pajerowski, Ruidan Zhong, Xianghan Xu, N. P. Armitage, Robert Cava, Collin Broholm

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17 pages, 6 figures
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AI总结：

本研究利用中子散射技术，在三角晶格反铁磁体 K$_2$Co(SeO$_3$)$_2$ 中通过自旋-玻色子映射，揭示了伴随强烈量子涨落的超固态相图，并发现了两种超固相及它们之间的 1/3 磁化平台。

摘要：

超固体是一种表现出超流性和固态双重特征的量子纠缠物质态。理论预测，在三角晶格上具有排斥相互作用的硬核玻色子在半填充和接近完全填充时可以形成超固相。利用玻色子与自旋-$\frac{1}{2}$自由度之间的精确映射，我们在交换常数 $J_z = 2.96(2)$~meV 和 $J_{\perp} = 0.21(3)$~meV 的自旋-$\frac{1}{2}$ 三角晶格反铁磁体 \K212 中研究了这些相。在零场下，中子衍射揭示了在 $T<15$~K 时准二维 $\sqrt{3}\times\sqrt{3}$ 磁序伴随 $Z_3$ 平移对称性破缺（固态）的逐渐发展，但在 $T=0.3$~K 时振幅减少了 44(5)%，表明存在强烈的量子涨落。这些涨落明显体现在 $\hslashω_n\approx n\times J_z$（其中 $n=0,1,2,3$）的连续中子散射等距带中。最低能量（$n=0$）的依赖 $\bf Q$ 的连续谱具有较低的共振边缘，并包含在 K $(\frac{1}{3}\frac{1}{3})$ 处的准弹性分量，这与 $U(1)$ 自旋转对称性破缺（玻色子超流性）一致。竞争的不稳定性明显体现在 M $(\frac{1}{2}0)$ 和 $\frac{1}{2}$K $(\frac{1}{6}\frac{1}{6})$ 处的软化但有限能模式中。对于几乎使磁化饱和、对应于几乎用玻色子填满晶格的 $\bf c$ 轴取向磁场 $17~{\rm T} <μ_0 H< 21~{\rm T}$，我们发现了一个与第二种超固体一致的新相。这些相被支持相干自旋波的显著 1/3 磁化平台隔开，我们由此确定了自旋哈密顿量。

英文摘要：

A supersolid is a quantum-entangled state of matter exhibiting the dual characteristics of superfluidity and solidity. Theory predicts that hard-core bosons with repulsive interactions on a triangular lattice can form supersolid phases at half filling and near complete filling. Leveraging an exact mapping between bosons and spin-$\frac{1}{2}$ degrees of freedom, we investigate these phases in the spin-$\frac{1}{2}$ triangular-lattice antiferromagnet \K212 with exchange constants $J_z = 2.96(2)$~meV and $J_{\perp} = 0.21(3)$~meV. At zero field, neutron diffraction reveals the gradual development for $T<15$~K of quasi-two-dimensional $\sqrt{3}\times\sqrt{3}$ magnetic order with $Z_3$ translational symmetry breaking (solidity) albeit with 44(5)% reduced amplitude at $T=0.3$~K indicating strong quantum fluctuations. These are apparent in equidistant bands of continuum neutron scattering for $\hslashω_n\approx n\times J_z$, where $n=0,1,2,3$. The lowest energy ($n=0$) $\bf Q$-dependent continuum has a lower resonant edge and includes a quasi-elastic component at K $(\frac{1}{3}\frac{1}{3})$ consistent with broken $U(1)$ spin rotational symmetry (boson superfluidity). Competing instabilities are apparent in soft albeit finite-energy modes at M $(\frac{1}{2}0)$ and at $\frac{1}{2}$K $(\frac{1}{6}\frac{1}{6})$. For $\bf c$-axis-oriented magnetic fields $17~{\rm T} <μ_0 H< 21~{\rm T}$ that almost saturate the magnetization, corresponding to nearly filling the lattice with bosons, we find a new phase consistent with a second supersolid. These phases are separated by a pronounced 1/3 magnetization plateau that supports coherent spin waves, from which we determine the spin Hamiltonian.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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