Electrical field tuning of magneto-Raman scattering in monolayer graphene

In this work, we report the electrical field tuning of magneto-phonon resonance in monolayer graphene under magnetic fields up to 9 T. It is found that the carrier concentration can drastically affect the G (E-2g) phonon response to a varying magnetic field through a pronounced magneto-phonon resonance (MPR). In charge neutral or slightly doped monolayer graphene, both the energy and the line width of the E-2g phonon show clear variation with magnetic fields. This is attributed to magneto-phonon resonance between magnetoexcitations and the E-2g phonons. In contrast, when the Fermi level of the monolayer graphene is far away from the Dirac point, the G band shows weak magnetic dependence and exhibits a symmetric line-shape. This suggests that the magneto-phonon coupling around 4 T has been switched off due to the Pauli blocking of the inter-Landau level excitations. Moreover, the G band asymmetry caused by Fano resonance between excitonic many-body states and the E-2g phonons is observed. This work offers a way to study the magnetoexcitation phonon interaction of materials through magneto-Raman spectroscopy with an external electrical field.