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arXiv 2009.01711cond-mat.str-el
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戈薇反铁磁体中的量子半孤儿

Quantum half-orphans in kagome antiferromagnets

Pranay Patil, Fabien Alet, Sylvain Capponi, Kedar Damle

摘要:

我们数值研究了自旋$S$海森堡反铁磁体中非磁性杂质(空位)对kagomé晶格的影响。对于一个范围内的低,但非零的温度,和自旋值,向下延伸到$S=2$,我们发现,磁化响应外部磁场是一致的应急“半孤儿”自由度,预计将占主导地位的响应相应的经典磁铁在一个类似的温度范围内,每当有两个空缺在同一个三角形的响应。具体地说,对于我们所考虑的所有自旋值(从$S=1/2$到$S=4$),在这样一个有两个空位的三角形上,孤自旋的局部磁化率有很大的增强;在均匀磁场$h$的存在下,这种孤自旋在有效场$h/2$中有效地表现为几乎自由的自旋$S$。非常值得注意的是,在零温度极限下,存在半孤儿的基态具有非零的总自旋值$S_{GS}$,当$S\ge 2$。响应的这些定性方面与没有这种半孤儿自由度的稀释样品的更常规响应显著不同。我们将讨论如何通过实验检查这些发现。

英文摘要:

We numerically study the effects of non-magnetic impurities (vacancies) in the spin-$S$ Heisenberg antiferromagnet on the kagomé lattice. For a range of low but nonzero temperatures, and spin values that extend down to $S=2$, we find that the magnetization response to an external magnetic field is consistent with the response of emergent "half-orphan" degrees of freedom that are expected to dominate the response of the corresponding classical magnet in a similar temperature range whenever there are two vacancies on the same triangle. Specifically, for all spin values we have considered (from $S=1/2$ to $S=4$), there is a large enhancement of the local susceptibility of the lone spin on such a triangle with two vacancies; in the presence of a uniform magnetic field $h$, this lone-spin behaves effectively as an almost free spin $S$ in an effective field $h/2$. Quite remarkably, in the zero temperature limit, the ground state in the presence of a half-orphan has a non-zero total spin value $S_{GS}$ that shows a trend similar to $S/2$ when $S\ge 2$. These qualitative aspects of the response differ strikingly from the more conventional response of diluted samples without such half-orphan degrees of freedom. We discuss how these findings could be checked experimentally.

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