Dr Edward McCann

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Research Overview

Condensed matter theory

Electronic properties of nanostructures

Graphene

Click here for an introductory talk about graphene, given to the general public in Lancaster City centre.

Click here for another introductory talk about graphene, given to the local branch of the Institute of Physics.

My research lies in the area of theoretical condensed matter physics. I'm particularly interested in the electronic properties of nanostructures and graphene. In small structures at low temperature, the quantum mechanics of electrons can be very important: they display wave-like properties including interference effects. This topic - the behaviour of electrons in phase coherent structures - is called mesoscopic physics. In the 1980s and 1990s, mesoscopic physics was studied in metals and semiconductors, but, recently, novel mesoscopic phenomena have been discovered in new materials including carbon nanotubes and graphene. The focus of my present research is to understand how electrons behave in graphene and related materials, including bilayer graphene and graphene multilayers.

Research Interests

Bilayer graphene

My major contribution - with colleague Volodya Fal'ko - was to show that low-energy electrons in bilayer graphene are massive chiral fermions. Their properties are unique: a quadratic energy-momentum dispersion with an unusual type of chirality (connection between the direction of pseudospin and momentum). They have a peculiar energy level spectrum in a magnetic field, including a double-degenerate zero-energy Landau level incorporating two different orbital states with the same energy. This means that, taking into account spin and valley degeneracies, the zero-energy Landau level in a bilayer is 8-fold degenerate, as compared to the 4-fold degeneracy of other bilayer states and the 4-fold degeneracy of all Landau levels in a monolayer. This led to a joint publication with the Manchester experimental mesoscopic physics group, who observed that the sequence of plateaus in the density dependence of the quantum Hall effect conductivity σ_xy is different from that of Dirac-type quasiparticles in a graphite monolayer and of non-chiral carriers in conventional semiconductor structures. This experiment confirmed the low-energy theory.

We predicted that it is possible to open a band gap in the energy bands of bilayer graphene. Subsequently, I developed a simple model that describes how the charge carrier density and the gap are tuneable with a gate or with doping. This model is useful because it helps experimentalists to understand the effect of gate potentials on the band structure of bilayer graphene devices.

For an introduction to the theory of electrons in monolayer and bilayer graphene, see my tutorial-style paper (suitable for advanced undergraduate, masters or postgraduate students), published as a chapter in Graphene Nanoelectronics: Metrology, Synthesis, Properties and Applications, pages 237-275 (Springer-Verlag Berlin Heidelberg 2012).

For more information about bilayer graphene in general, I recently co-authored a review paper, published as Rep. Prog. Phys. 76, 056503 (2013).

Weak localisation magnetoresistance in graphene

The chiral nature of electrons in graphene suppresses backscattering and, thus, can be expected to cause weak antilocalisation and a positive weak-field magnetoresistance. However, this can be true only for purely potential scattering, while any violation of the hexagonal symmetry by static disorder in a realistic graphene sheet or by edges in a narrow wire tends to restore conventional negative magnetoresistance. We showed this by evaluating the dependence of the magnetoresistance of graphene on relaxation rates associated with various possible ways of breaking the high original symmetry of the system. The resulting formula has been used widely to analyse experiments. Recently, we modelled the influence of spin-orbit coupling on weak localisation in graphene.

Trilayer graphene and graphene multilayers

With Mikito Koshino of Tohoku University, Sendai, Japan, I have modelled the electronic properties of graphene trilayers and multilayers. Their properties are sensitive to the way in which the graphene layers are stacked and the way in which external gate voltages, for example, break the layer symmetry. Please see my publication list for further details. In 2011, we organised two workshops, in Lancaster and Windermere, to promote UK-Japan scientific collaboration.

Recently, we wrote a paper with experimental colleagues, led by the group of Jeanie Lau at University of California, Riverside, in which the experiments observed dramatically different transport properties in trilayers with different stacking as well as peculiar behaviour in magnetic fields.

PhD Supervision Interests

There are projects available in the theory and modelling of the electronic properties of graphene - see research interests for more information about active research topics. Please feel free to contact me at the above email address for further details.

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Insulating state in tetralayers reveals an even-odd interaction effect in multilayer graphene
Grushina, A.L., Ki, D., Koshino, M., Nicolet, A.A.L., Faugeras, C., McCann, E., Potemski, M., Morpurgo, A.F. 3/03/2015 In: Nature Communications. 6, 7 p.
Journal article

Dirac edges of fractal magnetic minibands in graphene with hexagonal moire superlattices
Chen, X., Wallbank, J., Patel, A.A., Mucha-Kruczynski, M., McCann, E., Falko, V. 5/02/2014 In: Physical Review B. 89, 7, 5 p.
Journal article

The electronic properties of bilayer graphene
McCann, E., Koshino, M. 19/04/2013 In: Reports on Progress in Physics. 76, 5, 28 p.
Journal article

Multilayer graphenes with mixed stacking structure: Interplay of Bernal and rhombohedral stacking
Koshino, M., McCann, E. 22/01/2013 In: Physical Review B. 87, 4, 12 p.
Journal article

Evidence for spin memory in the electron phase coherence in graphene
Kozikov, A.A., Horsell, D.W., McCann, E., Falko, V. 23/07/2012 In: Physical Review B. 86, 4, 5 p.
Journal article

z -> -z Symmetry of Spin-Orbit Coupling and Weak Localization in Graphene
McCann, E., Falko, V. 20/04/2012 In: Physical Review Letters. 108, 16, p. -. 5 p.
Journal article

Electronic properties of monolayer and bilayer graphene
McCann, E. 2012 In: Graphene Nanoelectronics. Berlin Heidelberg : Springer Verlag p. 237-275. 39 p. ISBN: 978-3-642-20467-8. Electronic ISBN: 978-3-642-22984-8.
Chapter

Stacking-dependent band gap and quantum transport in trilayer graphene
Bao, W., Jing, L., Velasco Jr, J., Lee, Y., Liu, G., Tran, D., Standley, B., Aykol, M., Cronin, S.B., Smirnov, D., Koshino, M., McCann, E., Bockrath, M., Lau, C.N. 12/2011 In: Nature Physics. 7, 12, p. 948-952. 5 p.
Journal article

Manifestation of LO-LA phonons in Raman scattering in graphene
Ferone, R., Wallbank, J.R., Zolyomi, V., McCann, E., Falko, V. 1/08/2011 In: Solid State Communications. 151, 16, p. 1071-1074. 4 p.
Journal article

Landau level spectra and the quantum Hall effect of multilayer graphene
Koshino, M., McCann, E. 27/04/2011 In: Physical Review B. 83, 16, 9 p.
Journal article

Comment on “Screening in gated bilayer graphene”
Fogler, M.M., McCann, E. 22/11/2010 In: Physical Review B. 82, 19, 4 p.
Journal article

Spin-orbit coupling and broken spin degeneracy in multilayer graphene
McCann, E., Koshino, M. 15/06/2010 In: Physical Review B. 81, 24, 4 p.
Journal article

Parity and valley degeneracy in multilayer graphene
Koshino, M., McCann, E. 12/03/2010 In: Physical Review B. 81, 11, 6 p.
Journal article

Electron-hole asymmetry and energy gaps in bilayer graphene
Mucha-Kruczynski, M., McCann, E., Falko, V. 4/03/2010
Scientific review

Staying or going? Chirality decides!
McCann, E. 23/11/2009 In: Physics. 2, p. 98.
Journal article

Trigonal warping and Berry’s phase Npi in ABC-stacked multilayer graphene.
Koshino, M., McCann, E. 15/10/2009 In: Physical Review B. 80, 16, p. 165409.
Journal article

On spectral properties of bilayer graphene: the effect of an SiC substrate and infrared magneto-spectroscopy
Mucha Kruczynski, M., Abergel, D.S.L., McCann, E., Falko, V. 26/08/2009 In: Journal of Physics: Condensed Matter. 21, 34, 5 p.
Journal article

The influence of interlayer asymmetry on the magnetospectroscopy of bilayer graphene.
Mucha-Kruczynski, M., McCann, E., Falko, V. 07/2009 In: Solid State Communications. 149, 27-28, p. 1111-1116. 6 p.
Journal article

Pseudospin valve in bilayer graphene : towards graphene-based pseudospintronics.
San-Jose, P., Prada, E., McCann, E., Schomerus, H. 18/06/2009 In: Physical Review Letters. 102, 24, p. 247204.
Journal article

Gate-induced interlayer asymmetry in ABA-stacked trilayer graphene.
Koshino, M., McCann, E. 15/03/2009 In: Physical Review B. 79, 12, p. 125443.
Journal article

Tunable graphene system with two decoupled monolayers
Schmidt, H., Luedtke, T., Barthold, P., McCann, E., Falko, V., Haug, R.J. 27/10/2008 In: Applied Physics Letters. 93, 17, 3 p.
Journal article

Characterization of graphene through anisotropy of constant-energy maps in angle-resolved photoemission.
Mucha-Kruczyński, M., Tsyplyatyev, O., Grishin, A., McCann, E., Falko, V., Bostwick, A., Rotenberg, E. 15/05/2008 In: Physical Review B. 77, 19, p. 195403.
Journal article

Interlayer asymmetry gap in the electronic band structure of bilayer graphene.
McCann, E. 11/2007 In: physica status solidi (b). 244, 11, p. 4112-4117. 6 p.
Journal article

QHE and far infra-red properties of bilayer graphene in a strong magnetic field.
Abergel, D.S.L., McCann, E., Falko, V. 09/2007 In: European Physical Journal - Special Topics. 148, 1, p. 105-115. 11 p.
Journal article

The low energy electronic band structure of bilayer graphene.
McCann, E., Abergel, D.S.L., Falko, V. 09/2007 In: European Physical Journal - Special Topics. 148, 1, p. 91-103. 13 p.
Journal article

Weak localization in monolayer and bilayer graphene.
Kechedzhi, K., McCann, E., Falko, V., Suzuura, H., Ando, T., Altshuler, B.L. 09/2007 In: European Physical Journal - Special Topics. 148, 1, p. 39-54. 16 p.
Journal article

Electrons in bilayer graphene.
McCann, E., Abergel, D.S.L., Fal’ko, V.I. 07/2007 In: Solid State Communications. 143, 1-2, p. 110-115. 6 p.
Journal article

Weak localization in graphene.
Fal’ko, V.I., Kechedzhi, K., McCann, E., Altshuler, B.L., Suzuura, H., Ando, T. 07/2007 In: Solid State Communications. 143, 1-2, p. 33-38. 6 p.
Journal article

Influence of trigonal warping on interference effects in bilayer graphene
Kechedzhi, K., Falko, V.I., McCann, E., Altshuler, B.L. 27/04/2007 In: Physical Review Letters. 98, 17, 4 p.
Journal article

Weak localisation magnetoresistance and valley symmetry in graphene.
McCann, E., Kechedzhi, K., Fal’ko, V.I., Suzuura, H., Ando, T., Altshuler, B.L. 6/10/2006 In: Physical Review Letters. 97, 14, p. 146805.
Journal article

Asymmetry gap in the electronic band structure of bilayer graphene.
McCann, E. 10/2006 In: Physical Review B. 74, 16, p. 161403.
Journal article

Landau level degeneracy and quantum Hall effect in a graphite bilayer.
McCann, E., Fal’ko, V.I. 3/03/2006 In: Physical Review Letters. 96, 8, p. 086805.
Journal article

Unconventional quantum Hall effect and Berry’s phase 2pi in bilayer graphene.
Novoselov, K.S., McCann, E., Morozov, S.V., Fal’ko, V.I., Katsnelson, M.I., Zeitler, U., Jiang, D., Schedin, F., Geim, A.K. 03/2006 In: Nature Physics. 2, 3, p. 177-180. 4 p.
Journal article

Degeneracy breaking and intervalley scattering due to short-ranged impurities in finite single-wall carbon nanotubes.
McCann, E., Fal’ko, V.I. 15/02/2005 In: Physical Review B. 71, 8, p. 085415.
Journal article

Symmetry properties of impurities in metallic single-wall carbon nanotubes.
McCann, E., Falko, V.I. 10/10/2004 In: International Journal of Modern Physics B. 18, 23-24, p. 3195-3212. 18 p.
Journal article

Symmetry of boundary conditions of the Dirac equation for electrons in carbon nanotubes.
McCann, E., Fal’ko, V.I. 7/04/2004 In: Journal of Physics: Condensed Matter. 16, 13, p. 2371-2379. 9 p.
Journal article

A tunnel junction between a ferromagnet and a normal metal: magnon-assisted contribution to thermopower and conductance
McCann, E., Falko, V. 01/2004 In: Journal of Magnetism and Magnetic Materials. 268, 1-2, p. 123-131. 9 p.
Journal article

Andreev reflection and subgap transport due to electron-magnon interactions in ferromagnet-superconductor junctions.
Tkachov, G., McCann, E., Falko, V. 10/11/2003 In: International Journal of Modern Physics B. 17, 28, p. 5001-5005. 5 p.
Journal article

Magnon-assisted transport and thermopower in ferromagnet-normal-metal tunnel junctions
McCann, E., Falko, V. 2003 In: Physical Review B. 68, 17, p. -. 4 p.
Journal article

Magnetothermopower and magnon-assisted transport in ferromagnetic tunnel junctions
McCann, E., Falko, V. 4/11/2002 In: Applied Physics Letters. 81, 19, p. 3609-3611. 3 p.
Journal article

Giant magnetothermopower of magnon-assisted transport in ferromagnetic tunnel junctions
McCann, E., Falko, V. 1/10/2002 In: Physical Review B. 66, 13, p. -. 8 p.
Journal article

Subgap transport in ferromagnet-superconductor junctions due to magnon-assisted Andreev reflection
Tkachov, G., McCann, E., Falko, V. 1/01/2002 In: Physical Review B. 65, 2, p. -. 15 p.
Journal article

Magnon-assisted Andreev transport across ferromagnet-superconductor junctions
McCann, E., Tkachov, G., Falko, V. 01/2002 In: Physica E: Low-dimensional Systems and Nanostructures. 12, 1-4, p. 938-941. 4 p.
Journal article

Magnon-assisted Andreev reflection in a ferromagnet-superconductor junction
McCann, E., Falko, V. 11/2001 In: EPL. 56, 4, p. 583-589. 7 p.
Journal article

Correlation-function spectroscopy of inelastic lifetime in heavily doped GaAs heterostructures
Konemann, J., Konig, P., Schmidt, T., McCann, E., Falko, V., Haug, R.J. 15/10/2001 In: Physical Review B. 64, 15, p. -. 12 p.
Journal article

Parametric correlations of local density-of-states fluctuations in disordered pillars, wires and films
McCann, E., Falko, V. 6/08/2001 In: Journal of Physics: Condensed Matter. 13, 31, p. 6633-6648. 16 p.
Journal article

Energy dependence of quasi-particle relaxation in a disordered Fermi liquid.
Schmidt, T., König, P., McCann, E., Falko, V.I., Haug, R.J. 8/01/2001 In: Physical Review Letters. 86, 2, p. 276-279. 4 p.
Journal article

Local density of states probed by single electron tunneling
Konemann, J., Konig, P., Schmidt, T., McCann, E., Falko, V., Haug, R.J. 2001 In: Electronic Correlations: From Meso- to Nano-Physics. Les Ulis : E D P SCIENCES p. 283-286. 4 p. ISBN: 2-86883-570-8.
Conference contribution

Magnon-assisted Andreev reflection in a ferromagnet-superconductor junction
Falko, V., Tkachov, G., McCann, E. 2001 In: Electronic Correlations: From Meso- to Nano-Physics. Les Ulis : E D P SCIENCES p. 147-152. 6 p.
Paper

Measurement of the energy dependence of phase relaxation by single electron tunneling
Konig, P., Konemann, J., Schmidt, T., McCann, E., Falko, V., Haug, R.J. 2001 In: Proceedings of the 25th International Conference on the Physics of Semiconductors : Osaka, Japan, September 17-22, 2000 . Berlin : Springer Verlag p. 1337-1338. 2 p. ISBN: 3-540-41778-8.
Conference contribution

Weak localization correction to the ferromagnet-superconductor interface resistance
McCann, E., Falko, V., Volkov, A.F., Lambert, C.J. 2000 In: Physical Review B. 62, 9, p. 6015-6020. 6 p.
Journal article

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