Orbital and interlayer skyrmion crystals in bilayer graphene

R. Côté, Wenchen Luo, Branko Petrov, Yafis Barlas, and A. H. MacDonald
Phys. Rev. B 82, 245307 – Published 7 December 2010

Abstract

A graphene bilayer in a transverse magnetic field has a set of Landau levels with energies E=±N(N+1)ωc, where ωc is the effective cyclotron frequency and N=0,1,2, All Landau levels, but N=0, are four times degenerate counting spin and valley degrees of freedom. The Landau level N=0 contains an octet of degenerate states spanned by the layer spinors [0,hn,X,σ(r)] in valley K and [hn,X,σ(r),0] in valley K, where hn,X,σ(r) is the electronic wave function (or orbital) in Landau level n=0,1 with guiding center index X and spin σ in the Landau gauge. At integer filling factors, Coulomb interactions produce a set of broken-symmetry states with partial or full alignment in space of the valley and orbital pseudospins. These quantum Hall pseudoferromagnetic states support topological charged excitations in the form of orbital and valley skyrmions. Away from integer fillings, these topological excitations can condense to form a rich variety of Skyrme crystals with interesting properties. We study in this paper different crystal phases that occur when an electric field is applied between the layers. We show that orbital skyrmions, in analogy with spin skyrmions, have a texture of electrical dipoles that can be controlled by an in-plane electric field. The modulation of electronic density in the crystalline phases is experimentally accessible through a scanning tunneling microscope measurement of their local density of states.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
7 More
  • Received 2 October 2010

DOI:https://doi.org/10.1103/PhysRevB.82.245307

©2010 American Physical Society

Authors & Affiliations

R. Côté1, Wenchen Luo1, Branko Petrov1, Yafis Barlas2, and A. H. MacDonald3

  • 1Département de Physique, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
  • 2National High Magnetic Field Laboratory and Department of Physics, The Florida State University, Tallahassee, Florida 32306, USA
  • 3Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 82, Iss. 24 — 15 December 2010

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review B

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×