An altermagnet is a newly discovered antiferromagnet, characterized by unique anisotropic spin-split energy bands. It has attracted tremendous interest because of its promising potential in information storage and processing. However, measuring the distinctive spin-split energy bands arising from altermagnetism remains a challenge. Here, we propose to employ the Coulomb drag to probe altermagnetism. In the Coulomb drag, an electric current in an active layer of electron gases can induce currents in a close but well-isolated passive layer, due to interlayer Coulomb interactions. We find that the Coulomb drag effects in altermagnets are highly sensitive to the orientation of the spin-split Fermi surfaces. As a result, transverse currents can be dragged in the passive layer, leading to Hall drag effects even in the absence of spin-orbit coupling, a feature quite different from all previous systems. More importantly, all the drag effects of altermagnets have unique angle dependence, which can be measured in a multiterminal setup to serve as signatures for altermagnetism. This proposal will inspire increasing explorations on emergent magnetism.

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• Electrical conductivity
• Quantum transport
• k dot p method