论文标题
平面内偏振磁体的热厅电导率的符号结构
Sign structure of thermal Hall conductivity for in-plane-field polarized Kitaev magnets
论文作者
论文摘要
在平面磁场存在下，在$α$ -rucl $ _3 $中以$α$ -rucl $ _3 $的出现出现已被视为Kitaev Spin液体的有力证据。除了量化外，热厅电导率的观察到的符号结构也与基塔伊夫模型的精确解决方案的预测一致。也就是说，当田间方向相对于热电流逆转时，热霍尔电导率发生了变化，该热电流垂直于蜂窝晶格上的三个最近的邻居键之一。另一方面，当沿键方向应用场时，它几乎为零。在这里，我们表明，在存在平面磁场的情况下，热厅电导率的这种特殊的符号结构是极化状态的通用特性。在这种情况下，热霍尔效应来自具有有限的Chern数字的拓扑结构，符号结构来自动量空间浆果曲率的对称性。使用具有键依赖性相互作用的逼真的自旋模型，我们表明，热霍尔电导率可以与实验中观察到的相当。因此，单独的符号结构不能为基塔耶夫旋转液体提供强大的理由。然而，随着镁贡献在零温度限制中消失，温度非常低的量化将是决定性的测试。
The appearance of half-quantized thermal Hall conductivity in $α$-RuCl$_3$ in the presence of in-plane magnetic fields has been taken as a strong evidence for Kitaev spin liquid. Apart from the quantization, the observed sign structure of the thermal Hall conductivity is also consistent with predictions from the exact solution of the Kitaev model. Namely, the thermal Hall conductivity changes sign when the field direction is reversed with respect to the heat current, which is perpendicular to one of the three nearest neighbor bonds on the honeycomb lattice. On the other hand, it is almost zero when the field is applied along the bond direction. Here, we show that such a peculiar sign structure of the thermal Hall conductivity is a generic property of the polarized state in the presence of in-plane magnetic-fields. In this case, thermal Hall effect arises from topological magnons with finite Chern numbers and the sign structure follows from the symmetries of the momentum space Berry curvature. Using a realistic spin model with bond-dependent interactions, we show that the thermal Hall conductivity can have a magnitude comparable to that observed in the experiments. Hence the sign structure alone cannot make a strong case for Kitaev spin liquid. The quantization at very low temperatures, however, will be a decisive test as the magnon contribution vanishes in the zero temperature limit.
