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Greenaway MT, Kumaravadivel P, Wengraf J, Ponomarenko LA, Berdyugin AI, Li J, Edgar JH, Kumar RK, Geim AK, Eaves L. Graphene's non-equilibrium fermions reveal Doppler-shifted magnetophonon resonances accompanied by Mach supersonic and Landau velocity effects. Nat Commun 2021; 12:6392. [PMID: 34737289 PMCID: PMC8568928 DOI: 10.1038/s41467-021-26663-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 10/15/2021] [Indexed: 11/21/2022] Open
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. Magneto-oscillations have revealed many interesting phenomena in graphene and quantum Hall systems, but they are typically measured at low currents and in equilibrium. Here, the authors report several non-equilibrium quantum effects observed in magneto-oscillations in graphene at high currents.
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Affiliation(s)
- M T Greenaway
- Department of Physics, Loughborough University, Loughborough, LE11 3TU, UK. .,School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK.
| | - P Kumaravadivel
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - J Wengraf
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,Department of Physics, University of Lancaster, Lancaster, LA1 4YW, UK
| | - L A Ponomarenko
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,Department of Physics, University of Lancaster, Lancaster, LA1 4YW, UK
| | - A I Berdyugin
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - J Li
- Tim Taylor Department of Chemical Engineering, Kansas State University, Manhattan, KS, 66506, USA
| | - J H Edgar
- Tim Taylor Department of Chemical Engineering, Kansas State University, Manhattan, KS, 66506, USA
| | - R Krishna Kumar
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - A K Geim
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - L Eaves
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK. .,School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.
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Yang W, Graef H, Lu X, Zhang G, Taniguchi T, Watanabe K, Bachtold A, Teo EHT, Baudin E, Bocquillon E, Fève G, Berroir JM, Carpentier D, Goerbig MO, Plaçais B. Landau Velocity for Collective Quantum Hall Breakdown in Bilayer Graphene. PHYSICAL REVIEW LETTERS 2018; 121:136804. [PMID: 30312074 DOI: 10.1103/physrevlett.121.136804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Indexed: 06/08/2023]
Abstract
Breakdown of the quantum Hall effect (QHE) is commonly associated with an electric field approaching the inter-Landau-level (LL) Zener field, the ratio of the Landau gap and the cyclotron radius. Eluded in semiconducting heterostructures, in spite of extensive investigation, the intrinsic Zener limit is reported here using high-mobility bilayer graphene and high-frequency current noise. We show that collective excitations arising from electron-electron interactions are essential. Beyond a noiseless ballistic QHE regime a large super-Poissonian shot noise signals the breakdown via inter-LL scattering. The breakdown is ultimately limited by collective excitations in a regime where phonon and impurity scattering are quenched. The breakdown mechanism can be described by a Landau critical velocity as it bears strong similarities with the roton mechanism of superfluids. In addition, we show that breakdown is a precursor of an electric-field induced QHE-metal transition.
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Affiliation(s)
- W Yang
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, PSL University, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 24 rue Lhomond, 75005 Paris, France
| | - H Graef
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, PSL University, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 24 rue Lhomond, 75005 Paris, France
- CINTRA, UMI 3288, CNRS/NTU/Thales, Research Techno Plaza, 50 Nanyang Drive, Singapore 637553 Singapore
- Nanyang Technological University, School of Electrical and Electronic Engineering, 50 Nanyang Ave, Singapore 639798, Singapore
| | - X Lu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - G Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - T Taniguchi
- Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - K Watanabe
- Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - A Bachtold
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
| | - E H T Teo
- Nanyang Technological University, School of Electrical and Electronic Engineering, 50 Nanyang Ave, Singapore 639798, Singapore
| | - E Baudin
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, PSL University, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 24 rue Lhomond, 75005 Paris, France
| | - E Bocquillon
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, PSL University, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 24 rue Lhomond, 75005 Paris, France
| | - G Fève
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, PSL University, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 24 rue Lhomond, 75005 Paris, France
| | - J-M Berroir
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, PSL University, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 24 rue Lhomond, 75005 Paris, France
| | - D Carpentier
- University of Lyon, ENS de Lyon, University Claude Bernard, CNRS, Laboratoire de Physique, Lyon F-69342, France
| | - M O Goerbig
- Laboratoire de Physique des Solides, CNRS UMR 8502, University Paris-Sud, Université Paris-Saclay, F-91405 Orsay Cedex, France
| | - B Plaçais
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, PSL University, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 24 rue Lhomond, 75005 Paris, France
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