Orbital magnetic susceptibility of finite-sized graphene

We study the orbital magnetism of graphene ribbon in the effective-mass approximation, to figure out the finite-size effect on the singular susceptibility known in the bulk limit. We find that the susceptibility at T = 0 oscillates between diamagnetism and paramagnetism as a function of Fermi energy, in accordance with the subband structure formed by quantum confinement. In increasing T, the oscillation rapidly disappears once the thermal broadening energy exceeds the subband spacing, and the susceptibility approaches the bulk limit i.e., a thermally broadened diamagnetic peak centered at zero energy point. The electric current supporting the diamagnetism is found to flow near the edge with a depth which proportional to reciprocal of T, with v being the band velocity, while at T = 0 the current distribution spreads entirely in the sample reflecting the absence of the characteristic wavelength in graphene. The result is applied to estimate the three-dimensional random-stacked multilayer graphene, where we show that the external magnetic field is significantly screened inside the sample in low temperatures, in a much stronger manner than in graphite

Anisotropic Superconducting Spin Transport at Magnetic Interfaces

We present a theoretical investigation of anisotropic superconducting spin transport at a magnetic interface between a p-wave superconductor and a ferromagnetic insulator. Our formulation describes the ferromagnetic resonance modulations due to spin-triplet current generation, including the frequency shift and enhanced Gilbert damping, in a unified manner. We find that the Cooper pair symmetry is detectable from the qualitative behavior of the ferromagnetic resonance modulation. Our theory paves the way toward anisotropic superconducting spintronics.Comment: 7 pages, 7 figures, 2 table