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Supplementary information files for Graphene’s non-equilibrium fermions reveal Doppler-shifted magnetophonon resonances accompanied by Mach supersonic and Landau velocity effects

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posted on 22.11.2021, 12:12 by Mark GreenawayMark Greenaway, P Kumaravadivel, J Wengraf, LA Ponomarenko, AI Berdyugin, J Li, JH Edgar, R Krishna Kumar, AK Geim, L Eaves
Supplementary files for article Graphene’s non-equilibrium fermions reveal Doppler-shifted magnetophonon resonances accompanied by Mach supersonic and Landau velocity effects.

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.

Funding

Quantum dynamics of electrons in emerging van der Waals devices

Engineering and Physical Sciences Research Council

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Designing and exploring new quantum materials based on Fermi surface topological transitions

Engineering and Physical Sciences Research Council

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Lloyd’s Register Foundation

Office of Naval Research (award no. N00014-20-1-2474)

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