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arXiv 1807.07071cond-mat.str-elcond-mat.mtrl-sciquant-ph
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反铁磁海森堡kagome模型Schwinger-boson平均场论理论中自旋能隙随温度的快速填充

Rapid filling of the spin gap with temperature in the Schwinger-boson mean-field theory of the antiferromagnetic Heisenberg kagome model

Jad C. Halimeh, Rajiv R. P. Singh

摘要:

利用Schwinger-boson平均场论,计算了自旋$1/2$反铁磁海森堡kagome模型在带隙$\mathbb{Z}_2$自旋液相Anglomeres中的低温动态自旋结构因子$0<T\ll J$.我们发现光谱间隙随着温度迅速填充,其中稳健的低能光谱权重由$Δ/3$的温度发展,其中自旋间隙为$2Δ$(即,$Δ$是自旋能隙)。这是由于自旋子的去限制导致了仅由$\exp(-Δ/T)$抑制的项。在更高的温度下,自旋子密度迅速增加,导致Schwinger-boson平均场方法的崩溃。我们认为,如果可以通过中子散射实验获得的不含杂质的光谱函数的kagome赫伯茨米特,温度依赖性的子隙重量可以提供不同的签名的$\mathbb{Z}_2$量子自旋液体。

英文摘要:

Using Schwinger-boson mean-field theory, we calculate the dynamic spin structure factor at low temperatures $0<T\ll J$ for the spin-$1/2$ antiferromagnetic Heisenberg kagome model, within the gapped $\mathbb{Z}_2$ spin liquid phase Ansatz. We find that the spectral gap rapidly fills with temperature, with robust low-energy spectral weight developing by a temperature of $Δ/3$, where the spin gap is $2Δ$ (i.e., $Δ$ is the spinon gap), before any appreciable rise in spinon density or change in zero-temperature mean-field parameters. This is due to deconfinement of spinons which leads to terms suppressed only by $\exp(-Δ/T)$. At still higher temperatures, the spinon density increases rapidly leading to a breakdown of the Schwinger-boson mean-field approach. We suggest that if the impurity-free spectral functions can be obtained through neutron scattering experiments on kagome herbertsmithites, temperature dependence of the subgap weight can provide distinct signatures of a $\mathbb{Z}_2$ quantum spin liquid.

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