Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene

Keun Su Kim, Andrew L. Walter, Luca Moreschini, Thomas Seyller, Karsten Horn, Eli Rotenberg, Aaron Bostwick

Research output: Contribution to journalReview article

94 Citations (Scopus)

Abstract

Charge carriers in bilayer graphene are widely believed to be massive Dirac fermions that have a bandgap tunable by a transverse electric field. However, a full transport gap, despite its importance for device applications, has not been clearly observed in gated bilayer graphene, a long-standing puzzle. Moreover, the low-energy electronic structure of bilayer graphene is widely held to be unstable towards symmetry breaking either by structural distortions, such as twist, strain, or electronic interactions that can lead to various ground states. Which effect dominates the physics at low energies is hotly debated. Here we show both by direct band-structure measurements and by calculations that a native imperfection of bilayer graphene, a distribution of twists whose size is as small as ∼0.1, is sufficient to generate a completely new electronic spectrum consisting of massive and massless Dirac fermions. The massless spectrum is robust against strong electric fields, and has a unusual topology in momentum space consisting of closed arcs having an exotic chiral pseudospin texture, which can be tuned by varying the charge density. The discovery of this unusual Dirac spectrum not only complements the framework of massive Dirac fermions, widely relevant to charge transport in bilayer graphene, but also supports the possibility of valley Hall transport.

Original languageEnglish
Pages (from-to)887-892
Number of pages6
JournalNature materials
Volume12
Issue number10
DOIs
Publication statusPublished - 2013 Oct 1

Fingerprint

Graphite
Fermions
Crystal symmetry
Graphene
broken symmetry
graphene
fermions
Electric fields
electric fields
Charge density
Charge carriers
electronic spectra
complement
Band structure
Ground state
Electronic structure
valleys
Charge transfer
charge carriers
Momentum

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Mechanics of Materials
  • Condensed Matter Physics
  • Materials Science(all)
  • Chemistry(all)

Cite this

Kim, K. S., Walter, A. L., Moreschini, L., Seyller, T., Horn, K., Rotenberg, E., & Bostwick, A. (2013). Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene. Nature materials, 12(10), 887-892. https://doi.org/10.1038/nmat3717
Kim, Keun Su ; Walter, Andrew L. ; Moreschini, Luca ; Seyller, Thomas ; Horn, Karsten ; Rotenberg, Eli ; Bostwick, Aaron. / Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene. In: Nature materials. 2013 ; Vol. 12, No. 10. pp. 887-892.
@article{173f10f7df5144f181d0cc7d051a68f6,
title = "Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene",
abstract = "Charge carriers in bilayer graphene are widely believed to be massive Dirac fermions that have a bandgap tunable by a transverse electric field. However, a full transport gap, despite its importance for device applications, has not been clearly observed in gated bilayer graphene, a long-standing puzzle. Moreover, the low-energy electronic structure of bilayer graphene is widely held to be unstable towards symmetry breaking either by structural distortions, such as twist, strain, or electronic interactions that can lead to various ground states. Which effect dominates the physics at low energies is hotly debated. Here we show both by direct band-structure measurements and by calculations that a native imperfection of bilayer graphene, a distribution of twists whose size is as small as ∼0.1, is sufficient to generate a completely new electronic spectrum consisting of massive and massless Dirac fermions. The massless spectrum is robust against strong electric fields, and has a unusual topology in momentum space consisting of closed arcs having an exotic chiral pseudospin texture, which can be tuned by varying the charge density. The discovery of this unusual Dirac spectrum not only complements the framework of massive Dirac fermions, widely relevant to charge transport in bilayer graphene, but also supports the possibility of valley Hall transport.",
author = "Kim, {Keun Su} and Walter, {Andrew L.} and Luca Moreschini and Thomas Seyller and Karsten Horn and Eli Rotenberg and Aaron Bostwick",
year = "2013",
month = "10",
day = "1",
doi = "10.1038/nmat3717",
language = "English",
volume = "12",
pages = "887--892",
journal = "Nature Materials",
issn = "1476-1122",
publisher = "Nature Publishing Group",
number = "10",

}

Kim, KS, Walter, AL, Moreschini, L, Seyller, T, Horn, K, Rotenberg, E & Bostwick, A 2013, 'Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene', Nature materials, vol. 12, no. 10, pp. 887-892. https://doi.org/10.1038/nmat3717

Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene. / Kim, Keun Su; Walter, Andrew L.; Moreschini, Luca; Seyller, Thomas; Horn, Karsten; Rotenberg, Eli; Bostwick, Aaron.

In: Nature materials, Vol. 12, No. 10, 01.10.2013, p. 887-892.

Research output: Contribution to journalReview article

TY - JOUR

T1 - Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene

AU - Kim, Keun Su

AU - Walter, Andrew L.

AU - Moreschini, Luca

AU - Seyller, Thomas

AU - Horn, Karsten

AU - Rotenberg, Eli

AU - Bostwick, Aaron

PY - 2013/10/1

Y1 - 2013/10/1

N2 - Charge carriers in bilayer graphene are widely believed to be massive Dirac fermions that have a bandgap tunable by a transverse electric field. However, a full transport gap, despite its importance for device applications, has not been clearly observed in gated bilayer graphene, a long-standing puzzle. Moreover, the low-energy electronic structure of bilayer graphene is widely held to be unstable towards symmetry breaking either by structural distortions, such as twist, strain, or electronic interactions that can lead to various ground states. Which effect dominates the physics at low energies is hotly debated. Here we show both by direct band-structure measurements and by calculations that a native imperfection of bilayer graphene, a distribution of twists whose size is as small as ∼0.1, is sufficient to generate a completely new electronic spectrum consisting of massive and massless Dirac fermions. The massless spectrum is robust against strong electric fields, and has a unusual topology in momentum space consisting of closed arcs having an exotic chiral pseudospin texture, which can be tuned by varying the charge density. The discovery of this unusual Dirac spectrum not only complements the framework of massive Dirac fermions, widely relevant to charge transport in bilayer graphene, but also supports the possibility of valley Hall transport.

AB - Charge carriers in bilayer graphene are widely believed to be massive Dirac fermions that have a bandgap tunable by a transverse electric field. However, a full transport gap, despite its importance for device applications, has not been clearly observed in gated bilayer graphene, a long-standing puzzle. Moreover, the low-energy electronic structure of bilayer graphene is widely held to be unstable towards symmetry breaking either by structural distortions, such as twist, strain, or electronic interactions that can lead to various ground states. Which effect dominates the physics at low energies is hotly debated. Here we show both by direct band-structure measurements and by calculations that a native imperfection of bilayer graphene, a distribution of twists whose size is as small as ∼0.1, is sufficient to generate a completely new electronic spectrum consisting of massive and massless Dirac fermions. The massless spectrum is robust against strong electric fields, and has a unusual topology in momentum space consisting of closed arcs having an exotic chiral pseudospin texture, which can be tuned by varying the charge density. The discovery of this unusual Dirac spectrum not only complements the framework of massive Dirac fermions, widely relevant to charge transport in bilayer graphene, but also supports the possibility of valley Hall transport.

UR - http://www.scopus.com/inward/record.url?scp=84884571286&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84884571286&partnerID=8YFLogxK

U2 - 10.1038/nmat3717

DO - 10.1038/nmat3717

M3 - Review article

VL - 12

SP - 887

EP - 892

JO - Nature Materials

JF - Nature Materials

SN - 1476-1122

IS - 10

ER -

Kim KS, Walter AL, Moreschini L, Seyller T, Horn K, Rotenberg E et al. Coexisting massive and massless Dirac fermions in symmetry-broken bilayer graphene. Nature materials. 2013 Oct 1;12(10):887-892. https://doi.org/10.1038/nmat3717