Cyclotron resonance of the magnetic ratchet effect and second harmonic generation in bilayer graphene.

We model the magnetic ratchet effect in bilayer graphene in which a dc electric current is produced by an ac electric field of frequency $\omega$ in the presence of a steady in-plane magnetic field and inversion-symmetry breaking. In bilayer graphene, the ratchet effect is tunable by an external metallic gate which breaks inversion symmetry. For a tilted magnetic field, the perpendicular field component induces cyclotron motion with frequency $\omega_c$ and we find that the dc current displays cyclotron resonance at $\omega_c = \omega$, although this peak in the current is actually smaller than its value at $\omega_c = 0$. Second harmonic generation, however, is greatly enhanced by resonances at $\omega_c = \omega$ and $\omega_c = 2\omega$ for which the current is generally much larger than at $\omega_c = 0$.