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Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite
Physical Review X ( IF 11.6 ) Pub Date : 2020-12-23 , DOI: 10.1103/physrevx.10.041059
Masatoshi Akazawa , Masaaki Shimozawa , Shunichiro Kittaka , Toshiro Sakakibara , Ryutaro Okuma , Zenji Hiroi , Hyun-Yong Lee , Naoki Kawashima , Jung Hoon Han , Minoru Yamashita

We investigate the thermal-transport properties of the kagome antiferromagnet Cd-kapellasite (Cd-K). We find that a field-suppression effect on the longitudinal thermal conductivity κxx sets in below approximately 25 K. This field-suppression effect at 15 T becomes as large as 80% at low temperatures, suggesting a large spin contribution κxxsp in κxx. We also find clear thermal Hall signals in the spin liquid phase in all Cd-K samples. The magnitude of the thermal Hall conductivity κxy shows a significant dependence on the sample’s scattering time, as seen in the rise of the peak κxy value in almost linear fashion with the magnitude of κxx. On the other hand, the temperature dependence of κxy is similar in all Cd-K samples; κxy shows a peak at almost the same temperature of the peak of the phonon thermal conductivity κxxph which is estimated by κxx at 15 T. These results indicate the presence of a dominant phonon thermal Hall κxyph at 15 T. In addition to κxyph, we find that the field dependence of κxy at low fields turns out to be nonlinear at low temperatures, concomitantly with the appearance of the field suppression of κxx, indicating the presence of a spin thermal Hall κxysp at low fields. Remarkably, by assembling the κxx dependence of κxysp data of other kagome antiferromagnets, we find that, whereas κxysp stays a constant in the low-κxx region, κxysp starts to increase as κxx does in the high-κxx region. This κxx dependence of κxysp indicates the presence of both intrinsic and extrinsic mechanisms in the spin thermal Hall effect in kagome antiferromagnets. Furthermore, both κxyph and κxysp disappear in the antiferromagnetic ordered phase at low fields, showing that phonons alone do not exhibit the thermal Hall effect. A high field above approximately 7 T induces κxyph, concomitantly with a field-induced increase of κxx and the specific heat, suggesting a coupling of the phonons to the field-induced spin excitations as the origin of κxyph.

中文翻译:

Kagome反铁磁体Cd-Kapellasite中自旋和声子的热霍尔效应

我们研究了kagome反铁磁体Cd-kapellasite(Cd-K)的热传递性质。我们发现场抑制对纵向热导率的影响κXX 在低于25 K的温度下凝固。在15 T时的这种场抑制作用在低温下高达80%,表明自旋贡献很大 κXXSPκXX。我们还在所有Cd-K样品的自旋液相中发现了清晰的热霍尔信号。霍尔热导率的大小κXÿ 从峰的上升可以看出,它对样品的散射时间有很大的依赖性 κXÿ 值几乎呈线性,幅度为 κXX。另一方面,温度依赖性κXÿ 在所有Cd-K样品中均相似; κXÿ 在几乎与声子热导率峰相同的温度下显示峰 κXX酸碱度 据估计 κXX 在15 T时。这些结果表明存在显性声子热霍尔 κXÿ酸碱度 15 T时 κXÿ酸碱度,我们发现 κXÿ 在低温下的结果证明是非线性的,伴随着磁场抑制的出现。 κXX,表明存在自旋热霍尔 κXÿSP在低地。值得注意的是,通过组装κXX 的依赖 κXÿSP 我们发现其他kagome反铁磁体的数据 κXÿSP 在低位保持恒定κXX 地区, κXÿSP 开始增加 κXX 在高κXX地区。这个κXX 的依赖 κXÿSP表明在kagome反铁磁体的自旋热霍尔效应中同时存在内在和外在机理。此外,两者κXÿ酸碱度κXÿSP磁场在低磁场下在反铁磁有序相中消失,表明仅声子不会表现出热霍尔效应。高于约7 T的高场感应κXÿ酸碱度,伴随着磁场的增加 κXX 和比热,表明声子与场致自旋激发的耦合是 κXÿ酸碱度
更新日期:2020-12-23
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