Weakly coupled alternating S=12 chains in the distorted honeycomb lattice compound Na2Cu2TeO6

S. Gao, Ling-Fang Lin, A. May, B. Rai, Qiang Zhang, E. Dagotto, A. Christianson, M. Stone
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引用次数: 5

Abstract

Spin-1/2 chains with alternating antiferromagnetic (AF) and ferromagnetic (FM) couplings exhibit quantum entanglement like the integer-spin Haldane chains and might be similarly utilized for quantum computations. Such alternating AF-FM chains have been proposed to be realized in the distorted honeycomb-lattice compound Na$_2$Cu$_2$TeO$_6$, but to confirm this picture a comprehensive understanding of the exchange interactions including terms outside of the idealized model is required. Here we employ neutron scattering to study the spin dynamics in Na$_2$Cu$_2$TeO$_6$ and accurately determine the coupling strengths through the random phase approximation and density functional theory (DFT) approaches. We find the AF and FM intrachain couplings are the dominant terms in the spin Hamiltonian, while the interchain couplings are AF but perturbative. This hierarchy in the coupling strengths and the alternating signs of the intrachain couplings can be understood through their different exchange paths. Our results establish Na$_2$Cu$_2$TeO$_6$ as a weakly-coupled alternating AF-FM chain compound and reveal the robustness of the gapped ground state in alternating chains under weak interchain couplings.
变形蜂窝晶格化合物Na2Cu2TeO6中弱耦合交替S=12链
具有交替反铁磁(AF)和铁磁(FM)耦合的自旋-1/2链表现出像整数自旋霍尔丹链一样的量子纠缠,并且可能类似地用于量子计算。这种交替的AF-FM链已被提出在扭曲的蜂窝状晶格化合物Na$_2$Cu$_2$TeO$_6$中实现,但为了证实这一观点,需要对包括理想模型外的项在内的交换相互作用有全面的了解。本文采用中子散射方法研究了Na$_2$Cu$_2$TeO$_6$中的自旋动力学,并通过随机相位近似和密度泛函理论(DFT)方法精确地确定了耦合强度。我们发现自旋哈密顿量中AF和FM内耦合是主导项,而链间耦合是AF但微扰项。这种耦合强度的层次结构和链内耦合的交替符号可以通过它们不同的交换路径来理解。我们的结果证明Na$_2$Cu$_2$TeO$_6$是一个弱耦合的AF-FM交替链化合物,并揭示了在弱链间耦合下交替链中间隙基态的鲁棒性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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