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

Greenaway, M.T. and Kumaravadivel, P. and Wengraf, J. and Ponomarenko, L.A. and Berdyugin, A.I. and Li, J. and Edgar, J.H. and Kumar, R.K. and Geim, A.K. and Eaves, L. (2021) Graphene’s non-equilibrium fermions reveal Doppler-shifted magnetophonon resonances accompanied by Mach supersonic and Landau velocity effects. Nature Communications, 12 (1). ISSN 2041-1723

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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.

Item Type:
Journal Article
Journal or Publication Title:
Nature Communications
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/3100
Subjects:
ID Code:
162388
Deposited By:
Deposited On:
19 Nov 2021 12:09
Refereed?:
Yes
Published?:
Published
Last Modified:
22 Nov 2021 16:51