Fig. 6: Static skin effect.
a When ωcτ ≫ 1, bulk carriers whirl along cyclotron orbits numerous times without being scattered. This yields a semiclassical account of the large orbital magnetoresistance in compensated semimetals with ballistic carriers like Bi. The cyclotron orbits are interrupted at the edge of the sample (in green). When reflections are specular, magnetoresistance is canceled in this region. b In this semiclassical picture, the excess of conductance when the field is parallel to a surface arises thanks to additional conduction along dissipation-free edges. c In a larger magnetic field, the cyclotron edge is narrower and the difference between bulk and boundary conductivities is larger. Therefore, the conductivity profile is expected to evolve with increasing magnetic field. It is sketched for two different possibilities: (i) the conductivity inside the cyclotron edge does not evolve with depth (solid black line), and (ii) hybridization leads to a smooth variation across the cyclotron edge (red dashed line). Experimentally, the relative conductivity excess does not change above 0.2 T.
