J. H. Gronqvist, T. Stroucken, and S.W. Koch Optical signatures for...
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Optical signatures for strong coupling in graphene Bright excitonic signatures in the absorption spectrum indicates a strongly Coulomb correlated, gapped state. no Coulomb, shows band edge full calculation, excitons below band edge frequency absorption 0 0 momentum energy quasiparticle conduction band in strong-coupling phase bright excitons quasiparticle valence band Spectrum has clustered peaks. Clustering comes from coupling between two degenerate p states. Coupling is caused by Auger processes in the Coulomb interaction. Auger processes, antisymmetric particles-per- band preserved, symmetric Graphene in the strong-coupling phase has a broken sublattice symmetry, and a non-zero band gap. Calculated with gap equations, see poster \Strong coupling in graphene - conditions" by T.S., J.H.G., and S.W.K. intraband interband antisymmetric p states superimposed on ground state populations excite Light creates p states because of the symmetry of the light-matter coup- ling at the Dirac point. + similar terms light-matter matrix element Strong-coupling can be viewed either as populated Dirac bands, or quasiparticles with gapped bands. J. H. Gronqvist, T. Stroucken, and S.W. Koch 1. Department of Physics and Material Sciences Center, Philipps University Marburg, Germany 2. Department of Physics, Abo Akademi University, Finland 1 1,2 1 0 coupling strength c o n t i n u u m frequency Excite ground state p-like excitons at the Dirac point. Ground state Optical excitation Auger splitting band edge gap Excitons in absorption spectrum isotropic (Dirac band) populations in strong-coupling ground state Swicthing off the Auger terms gives degenerate exciton peaks. 0 Auger strength frequency 3 / 4 full Auger no Auger 1 / 4 1 / 2 Gradually turning the Auger terms back on lifts the degeneracy. Size of gap depends on coupling strength. Coupling smaller gap smaller excitons squeeze together. T. Stroucken, J. H. Gronqvist, and S. W. Koch, \Excitonic resonances as fingerprint of strong Coulomb coupling in graphene," J. Opt. Soc. Am. B 29 , A86 (2012) \Optical response and ground state of graphene," Phys. Rev. B 84 , 205445 (2011).
Transcript of J. H. Gronqvist, T. Stroucken, and S.W. Koch Optical signatures for...
Optical signatures for strong coupling in graphene
Bright excitonic signatures in theabsorption spectrum indicates a strongly Coulomb correlated, gapped state.
no Coulomb, shows band edge
full calculation,excitons below
band edge
frequency
abso
rption
0
0
momentum
ener
gy
quasiparticleconduction bandin strong-coupling
phase
brightexcitons
quasiparticlevalence band
Spectrum has clustered peaks. Clustering comes from coupling between two degenerate p states.
Coupling is caused by Auger processes in the Coulomb interaction.
Auger processes,antisymmetric
particles-per-band preserved, symmetric
Graphene in the strong-coupling phase has a broken sublattice symmetry, and a non-zero band gap.
Calculated with gap equations,see poster \Strong coupling in graphene - conditions" by T.S.,J.H.G., and S.W.K.
intrabandinterband
antisymmetric p states superimposed on ground
state populations
excite
Light creates p states because of the symmetry of the light-matter coup-ling at the Dirac point.
+ similar terms
light-matter matrix element
Strong-coupling
can be viewed either as populated Dirac bands, or quasiparticles with gapped bands.
J. H. Gronqvist, T. Stroucken, and S.W. Koch
1. Department of Physics and Material Sciences Center, Philipps University Marburg, Germany2. Department of Physics, Abo Akademi University, Finland
11,2 1
0
couplin
g stren
gth
c o n t i n u u m
frequency
Excite ground state p-like excitons at the Dirac point.
Ground state
Optical excitation
Auger splitting
band edge
gap
Excitons in absorption spectrum
isotropic (Dirac band) populations in strong-coupling
ground state
Swicthing off the Auger terms gives degenerate exciton peaks.
0
Auger
strength
frequency
3/4
fullAuger
noAuger
1/41/2
Gradually turning the Auger terms back on lifts the degeneracy.
Size of gapdepends on coupling strength. Coupling smaller gap smaller excitons squeeze together.
T. Stroucken, J. H. Gronqvist, and S. W. Koch, \Excitonic resonances as fingerprint of strong Coulomb coupling in graphene," J. Opt. Soc. Am. B 29, A86 (2012)\Optical response and ground state of graphene," Phys. Rev. B 84, 205445 (2011).
