Veyrat Arthur, Koepernik Klaus, Veyrat Louis, Shipunov Grigory, Kovalchuk Iryna, Aswartham Saicharan, Qu Jiang, Kumar Ankit, Ceccardi Michele, Caglieris Federico, Pérez Nicolás, Giraud Romain, Büchner Bernd, van den Brink Jeroen, Ortix Carmine, Dufouleur Joseph
Leibniz Institute for Solid State and Materials Research (IFW Dresden), Helmholtzstraße 20, Dresden, Germany.
Würzburg-Dresden Cluster of Excellence ct.qmat, Dresden, Germany.
Nat Commun. 2025 Jul 21;16(1):6711. doi: 10.1038/s41467-025-61059-8.
Topological materials, such as topological insulators or semimetals, usually not only reveal the non-trivial properties of their electronic wavefunctions through the appearance of stable boundary modes, but also through very specific electromagnetic responses. The anisotropic longitudinal magnetoresistance of Weyl semimetals, for instance, carries the signature of the chiral anomaly of Weyl fermions. However for topological nodal line semimetals-materials where the valence and conduction bands cross each other on one-dimensional curves in the three-dimensional Brillouin zone-such a characteristic has been lacking. Here we report the discovery of a peculiar charge transport effect generated by topological nodal lines in trigonal crystals: a dissipationless transverse signal in the presence of coplanar electric and magnetic fields, which we attribute to a Zeeman-induced conversion of topological nodal lines into Weyl nodes under infinitesimally small magnetic fields. We evidence this dissipationless topological response in trigonal PtBi persisting up to room temperature, consistent with the presence of extensive topological nodal lines in the band structure of this non-magnetic material. These findings provide a pathway to engineer Weyl nodes by arbitrary small magnetic fields and reveal that bulk topological nodal lines can exhibit non-dissipative transport properties.
拓扑材料，如拓扑绝缘体或半金属，通常不仅通过稳定边界模式的出现来揭示其电子波函数的非平凡性质，还通过非常特定的电磁响应来揭示。例如，外尔半金属的各向异性纵向磁阻带有外尔费米子手征反常的特征。然而，对于拓扑节线半金属（即价带和导带在三维布里渊区的一维曲线上相互交叉的材料），这种特征一直缺失。在此，我们报告在三角晶体中由拓扑节线产生的一种奇特电荷传输效应的发现：在共面电场和磁场存在下的无耗散横向信号，我们将其归因于在极小磁场下塞曼诱导的拓扑节线向外尔节点的转变。我们证明了这种无耗散拓扑响应在三角PtBi中持续到室温，这与这种非磁性材料能带结构中广泛存在的拓扑节线一致。这些发现提供了一种通过任意小磁场来调控外尔节点的途径，并揭示了体拓扑节线可以表现出无耗散输运性质。
