Abstract
Oscillatory magnetoresistance measurements on graphene have revealed a wealth of novel physics. These phenomena are typically studied at low currents. At high currents, electrons are driven far from equilibrium with the atomic lattice vibrations so that their kinetic energy can exceed the thermal energy of the phonons. Here, we report three non-equilibrium phenomena in monolayer graphene at high currents: (i) a “Doppler-like” shift and splitting of the frequencies of the transverse acoustic (TA) phonons emitted when the electrons undergo inter-Landau level (LL) transitions; (ii) an intra-LL Mach effect with the emission of TA phonons when the electrons approach supersonic speed, and (iii) the onset of elastic inter-LL transitions at a critical carrier drift velocity, analogous to the superfluid Landau velocity. All three quantum phenomena can be unified in a single resonance equation. They offer avenues for research on out-of-equilibrium phenomena in other two-dimensional fermion systems.
Highlights
Oscillatory magnetoresistance measurements on graphene have revealed a wealth of novel physics
The field-induced shifts and splittings in high-mobility GaAs quantum well (QW) heterostructures arise from inter-LL scattering by acoustic phonons of lower energy[6,7,8,9]
We search for non-equilibrium magneto-oscillations (NEMOs) using large area Hall bars of highpurity exfoliated monolayer graphene encapsulated between layers of exfoliated hexagonal boron nitride and mounted on a silicon oxide–silicon gate electrode; for further information regarding fabrication, see ref
Summary
Oscillatory magnetoresistance measurements on graphene have revealed a wealth of novel physics. In bulk n-type GaAs, fields F ~ 106 Vm−1 induce large shifts and splittings of the magnetophonon resonance (MPR) peaks due to scattering by 36 meV longitudinal optical phonons, along with quasi-elastic inter-Landau level (LL) transitions[3,4,5].
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