The emerging field of orbitronics aims to generate and control orbital angular momentum for information processing. Chiral crystals are promising orbitronic materials because they have been predicted to host monopole-like orbital textures, where the orbital angular momentum aligns isotropically with the electron’s crystal momentum. However, such monopoles have not yet been directly observed in chiral crystals. Here, we use circular dichroism in angle-resolved photoelectron spectroscopy to image orbital angular momentum monopoles in the chiral topological semimetals PtGa and PdGa. The spectra show a robust polar texture that rotates around the monopole as a function of photon energy. This is a direct consequence of the underlying magnetic orbital texture and can be understood from the interference of local atomic contributions. Moreover, we also demonstrate that the polarity of the monopoles can be controlled through the structural handedness of the host crystal by imaging orbital angular moment monopoles and antimonopoles in the two enantiomers of PdGa, respectively. Our results highlight the potential of chiral crystals for orbitronic device applications, and our methodology could enable the discovery of even more complicated nodal orbital angular momentum textures that could be exploited for orbitronics.

新兴的轨道电子学领域旨在生成和控制轨道角动量以进行信息处理。手性晶体是有前途的轨道电子材料，因为它们被预测具有类似单极子的轨道纹理，其中轨道角动量与电子的晶体动量各向同性地排列。然而，这种单极子尚未在手性晶体中直接观察到。在这里，我们使用角分辨光电子能谱中的圆二色性对手性拓扑半金属 PtGa 和 PdGa 中的轨道角动量单极子进行成像。光谱显示出强大的极性纹理，它作为光子能量的函数围绕单极子旋转。这是底层磁轨道结构的直接结果，可以从局部原子贡献的干扰来理解。此外，我们还通过分别对 PdGa 两种对映体中的轨道角矩单极子和反单极子进行成像，证明单极子的极性可以通过主晶体的结构旋向性来控制。我们的结果凸显了手性晶体在轨道电子器件应用中的潜力，我们的方法可以发现更复杂的节点轨道角动量纹理，可用于轨道电子学。