With alternating current (AC), electrons flow more at the outer surface of the wire rather than through the middle. The higher the frequency, the more the skin effect and the greater the resistance.

More information: Hang Zhou et al, Skin Effect of Nonlinear Optical Responses in Antiferromagnets, Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.133.236903 Provided by Chinese Academy ...