Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite
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 κ_{xx} sets in below approximately 25 K. This field-suppression effect at 15 T becomes as large as 80% at low temperat...
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American Physical Society
2020
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oai:doaj.org-article:c35ad21ac19e4479be50c3678f0297b22021-12-02T13:27:32ZThermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite10.1103/PhysRevX.10.0410592160-3308https://doaj.org/article/c35ad21ac19e4479be50c3678f0297b22020-12-01T00:00:00Zhttp://doi.org/10.1103/PhysRevX.10.041059http://doi.org/10.1103/PhysRevX.10.041059https://doaj.org/toc/2160-3308We 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 κ_{xx} 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 κ_{xx}^{sp} in κ_{xx}. We also find clear thermal Hall signals in the spin liquid phase in all Cd-K samples. The magnitude of the thermal Hall conductivity κ_{xy} shows a significant dependence on the sample’s scattering time, as seen in the rise of the peak κ_{xy} value in almost linear fashion with the magnitude of κ_{xx}. On the other hand, the temperature dependence of κ_{xy} is similar in all Cd-K samples; κ_{xy} shows a peak at almost the same temperature of the peak of the phonon thermal conductivity κ_{xx}^{ph} which is estimated by κ_{xx} at 15 T. These results indicate the presence of a dominant phonon thermal Hall κ_{xy}^{ph} at 15 T. In addition to κ_{xy}^{ph}, we find that the field dependence of κ_{xy} at low fields turns out to be nonlinear at low temperatures, concomitantly with the appearance of the field suppression of κ_{xx}, indicating the presence of a spin thermal Hall κ_{xy}^{sp} at low fields. Remarkably, by assembling the κ_{xx} dependence of κ_{xy}^{sp} data of other kagome antiferromagnets, we find that, whereas κ_{xy}^{sp} stays a constant in the low-κ_{xx} region, κ_{xy}^{sp} starts to increase as κ_{xx} does in the high-κ_{xx} region. This κ_{xx} dependence of κ_{xy}^{sp} indicates the presence of both intrinsic and extrinsic mechanisms in the spin thermal Hall effect in kagome antiferromagnets. Furthermore, both κ_{xy}^{ph} and κ_{xy}^{sp} 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 κ_{xy}^{ph}, concomitantly with a field-induced increase of κ_{xx} and the specific heat, suggesting a coupling of the phonons to the field-induced spin excitations as the origin of κ_{xy}^{ph}.Masatoshi AkazawaMasaaki ShimozawaShunichiro KittakaToshiro SakakibaraRyutaro OkumaZenji HiroiHyun-Yong LeeNaoki KawashimaJung Hoon HanMinoru YamashitaAmerican Physical SocietyarticlePhysicsQC1-999ENPhysical Review X, Vol 10, Iss 4, p 041059 (2020) |
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Physics QC1-999 |
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Physics QC1-999 Masatoshi Akazawa Masaaki Shimozawa Shunichiro Kittaka Toshiro Sakakibara Ryutaro Okuma Zenji Hiroi Hyun-Yong Lee Naoki Kawashima Jung Hoon Han Minoru Yamashita Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite |
| description |
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 κ_{xx} 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 κ_{xx}^{sp} in κ_{xx}. We also find clear thermal Hall signals in the spin liquid phase in all Cd-K samples. The magnitude of the thermal Hall conductivity κ_{xy} shows a significant dependence on the sample’s scattering time, as seen in the rise of the peak κ_{xy} value in almost linear fashion with the magnitude of κ_{xx}. On the other hand, the temperature dependence of κ_{xy} is similar in all Cd-K samples; κ_{xy} shows a peak at almost the same temperature of the peak of the phonon thermal conductivity κ_{xx}^{ph} which is estimated by κ_{xx} at 15 T. These results indicate the presence of a dominant phonon thermal Hall κ_{xy}^{ph} at 15 T. In addition to κ_{xy}^{ph}, we find that the field dependence of κ_{xy} at low fields turns out to be nonlinear at low temperatures, concomitantly with the appearance of the field suppression of κ_{xx}, indicating the presence of a spin thermal Hall κ_{xy}^{sp} at low fields. Remarkably, by assembling the κ_{xx} dependence of κ_{xy}^{sp} data of other kagome antiferromagnets, we find that, whereas κ_{xy}^{sp} stays a constant in the low-κ_{xx} region, κ_{xy}^{sp} starts to increase as κ_{xx} does in the high-κ_{xx} region. This κ_{xx} dependence of κ_{xy}^{sp} indicates the presence of both intrinsic and extrinsic mechanisms in the spin thermal Hall effect in kagome antiferromagnets. Furthermore, both κ_{xy}^{ph} and κ_{xy}^{sp} 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 κ_{xy}^{ph}, concomitantly with a field-induced increase of κ_{xx} and the specific heat, suggesting a coupling of the phonons to the field-induced spin excitations as the origin of κ_{xy}^{ph}. |
| format |
article |
| author |
Masatoshi Akazawa Masaaki Shimozawa Shunichiro Kittaka Toshiro Sakakibara Ryutaro Okuma Zenji Hiroi Hyun-Yong Lee Naoki Kawashima Jung Hoon Han Minoru Yamashita |
| author_facet |
Masatoshi Akazawa Masaaki Shimozawa Shunichiro Kittaka Toshiro Sakakibara Ryutaro Okuma Zenji Hiroi Hyun-Yong Lee Naoki Kawashima Jung Hoon Han Minoru Yamashita |
| author_sort |
Masatoshi Akazawa |
| title |
Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite |
| title_short |
Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite |
| title_full |
Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite |
| title_fullStr |
Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite |
| title_full_unstemmed |
Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite |
| title_sort |
thermal hall effects of spins and phonons in kagome antiferromagnet cd-kapellasite |
| publisher |
American Physical Society |
| publishDate |
2020 |
| url |
https://doaj.org/article/c35ad21ac19e4479be50c3678f0297b2 |
| work_keys_str_mv |
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