$d$-Wave Flat Fermi Surface in Altermagnets Enables Maximum Charge-to-Spin Conversion
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arXiv
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| Format: | Preprint |
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2025
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| author | Lai, Junwen Yu, Tianye Liu, Peitao Liu, Long Xing, Guozhong Chen, Xing-Qiu Sun, Yan |
| author_facet | Lai, Junwen Yu, Tianye Liu, Peitao Liu, Long Xing, Guozhong Chen, Xing-Qiu Sun, Yan |
| contents | Altermagnets combine antiferromagnetic order with ferromagnet-like spin splitting, a duality that unlocks ultrafast spin-dependent responses. This unique property creates unprecedented opportunities for spin-current generation, overcoming the intrinsic limitations of conventional spin-transfer and spin-orbit torque approaches in magnetic memory technologies. Here, we establish a fundamental relationship between Fermi surface geometry and time-reversal-odd ($\mathcal{T}$-odd) spin currents in altermagnets through combined model analysis and first-principles calculations. We demonstrate that a $d$-wave altermagnet with a flat Fermi surface can achieve a theoretical upper limit of charge-to-spin conversion efficiency (CSE) of 100%. This mechanism is realized in the newly discovered room-temperature altermagnetic metal KV$_2$O$_2$Se, which exhibits a CSE of $\sim$78% at the charge neutrality point, nearly double that of RuO$_2$, setting a new record for $\mathcal{T}$-odd CSE. Under electron doping, this efficiency further increases to $\sim$98%, approaching the theoretical limit. Our work advances the fundamental understanding of $\mathcal{T}$-odd spin currents via Fermi surface geometry engineering and provides key insights for developing next-generation altermagnet-based memory devices. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_07703 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | $d$-Wave Flat Fermi Surface in Altermagnets Enables Maximum Charge-to-Spin Conversion Lai, Junwen Yu, Tianye Liu, Peitao Liu, Long Xing, Guozhong Chen, Xing-Qiu Sun, Yan Materials Science Altermagnets combine antiferromagnetic order with ferromagnet-like spin splitting, a duality that unlocks ultrafast spin-dependent responses. This unique property creates unprecedented opportunities for spin-current generation, overcoming the intrinsic limitations of conventional spin-transfer and spin-orbit torque approaches in magnetic memory technologies. Here, we establish a fundamental relationship between Fermi surface geometry and time-reversal-odd ($\mathcal{T}$-odd) spin currents in altermagnets through combined model analysis and first-principles calculations. We demonstrate that a $d$-wave altermagnet with a flat Fermi surface can achieve a theoretical upper limit of charge-to-spin conversion efficiency (CSE) of 100%. This mechanism is realized in the newly discovered room-temperature altermagnetic metal KV$_2$O$_2$Se, which exhibits a CSE of $\sim$78% at the charge neutrality point, nearly double that of RuO$_2$, setting a new record for $\mathcal{T}$-odd CSE. Under electron doping, this efficiency further increases to $\sim$98%, approaching the theoretical limit. Our work advances the fundamental understanding of $\mathcal{T}$-odd spin currents via Fermi surface geometry engineering and provides key insights for developing next-generation altermagnet-based memory devices. |
| title | $d$-Wave Flat Fermi Surface in Altermagnets Enables Maximum Charge-to-Spin Conversion |
| topic | Materials Science |
| url | https://arxiv.org/abs/2506.07703 |