轨道能斯特效应的观测

中文摘要 AI 辅助

能斯特效应将温度梯度转化为横向电荷电流，是热电学的基础。其自旋类比——自旋能斯特效应——能够实现横向自旋电流的热产生，是自旋热电子学的核心。近期，轨道电流（自旋电流的轨道对应物）的发现将角动量输运扩展到了自旋之外，从而预言了轨道能斯特效应，即温度梯度驱动横向轨道电流。然而，该效应的实验证据一直缺乏。在此，我们报告在钛（Ti）中观测到轨道能斯特效应。利用钛上的镍（Ni）电极，我们检测到一种热致电压，该电压依赖于磁化方向，并与温度梯度呈线性关系。当镍被替换为Ni$_{81}$Fe$_{19}$，以及钛被替换为铬（Cr）时，该电压被强烈抑制，这提供了强有力的证据表明该信号源于轨道能斯特效应，而非反常能斯特或自旋能斯特效应。这些结果确立了热驱动的轨道输运，为轨道热电子学开辟了道路。

英文摘要

The Nernst effect, which converts a temperature gradient into a transverse charge current, is fundamental to thermoelectrics. Its spin analogue, the spin Nernst effect, enables thermal generation of transverse spin currents and is central to spin caloritronics. Recently, the discovery of orbital currents, the orbital counterpart of spin currents, has extended angular-momentum transport beyond spin, leading to the prediction of the orbital Nernst effect, in which a temperature gradient drives a transverse orbital current. However, experimental evidence for this effect has been lacking. Here, we report the observation of the orbital Nernst effect in Ti. Using Ni electrodes on Ti, we detect a thermally induced voltage that depends on the magnetization direction and scales linearly with the temperature gradient. This voltage is strongly suppressed both when Ni is replaced with Ni$_{81}$Fe$_{19}$ and when Ti is replaced with Cr, providing strong evidence that the signal originates from the orbital Nernst effect rather than the anomalous Nernst or spin Nernst effect. These results establish thermally driven orbital transport, opening a pathway toward orbital caloritronics.

发表机构

• Keio University（庆应义塾大学）
• National Institute for Materials Science（国立材料研究所）
• Uppsala University（乌普萨拉大学）
• The University of Tokyo（东京大学）

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