Graphene Research Paper

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  • Topic: Graphene, Quantum Hall effect, Condensed matter physics
  • Pages : 5 (586 words )
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  • Published : January 30, 2012
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The Nobel Prize in Physics 2010 was awarded jointly to: Andre Geim and Konstantin Novoselov (University of Manchester) "for groundbreaking experiments regarding the twodimensional material graphene"

The rise of graphene
A.K. Geim and K.S. Novoselov Nature Materials, vol. 6, March 2007 Presented by Angela Intermite Journal Club presentation 18/10/2010

Overview • Definition of graphene • History of a material that should not exist • Experimental evidence • Electronic structure • Electronic qualities • Electronic transport • Optical properties • Anomalous Quantum Hall Effect in monolayer and bilayer graphene • The mystery of the missing pie

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Graphene: a rising star

0D fullerenes

1D nanotubes

3D graphite

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The material that should not exist

L.D. Landau

Until 2004…

R. E. Peierls Angela Intermite

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The bridge between theory and experimental evidence
Graphene

• metastable state but strong interatomic bonds

1 layer Boron Nitride

no thermal fluctuations • crumpling in the third dimension

½ layer BSCCO

gain in elastic energy
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Graphene electronic structure: semimetal
Semiconductor with direct gap

Graphene

Semiconductor with indirect gap

Semimetal

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Electronic qualities: quasiparticles and ballistic transistors

Ballistic transistor: free flowing electrons are forced around a wedge-shaped obstacle in one direction or another, corresponding to a logical 1 or 0.

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Electronic transport

• High electron mobility: 15.000 cm2 V-1 s-1 • Resistivity 10-6 cm < silver • Minimum conductivity on the order of 4e2/h Angela Intermite The rise of graphene, 18/10/2010 9/16

Optical properties

• High opacity • Absorption of πa ≈ 2.3% white light • Saturation under strong excittion over visible to near-infrared region: suitable as absorber for mode locking of fiber lasers and ultrafast photonics

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Anomalous Quantum Hall Effect in monolayer graphene
Standard Quantum Hall Effect

Graphene Quantum Hall Effect

Quantization of graphene’s electronic spectrum in magnetic field B Angela Intermite The rise of graphene, 18/10/2010 11/16

Anomalous Quantum Hall Effect in bilayer graphene
Hamiltonian of bilayer graphene Monolayer graphene

Bilayer graphene Standard QHE can be recovered in bilayer graphene by the electric field effect, i.e. applying a gate voltage. Bilayer graphene + electric field

Unique material!

Angela Intermite

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The mystery of a missing pie
• σ →e2/h for n→0 • Low conductivity but no metal-semiconductor transition at low T. • Quantization of conductivity • Experimental limit of σ different from theoretical one→ the mystery of the missing pie

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Future possible applications
• Ballistic transistors • Integrated circuits • Quantum computers • Ultra fast photonics • Single molecule gas detection • Ancti bacteria devices •… Angela Intermite The rise of graphene, 18/10/2010 114/16

References
1. “The rise of graphene”, A.K. Geim and K.S. Novoselov, Nature materials, Vol. 6, March 2007 2. “ Room temperature quantum Hall Effect” K.S. Novoselov and al., Science, Vol. 315. no. 5817, p. 1379, March 2007 3. “The electronic properties of graphene”, A.H. Castro Neto et al., Rev of Mod Physics, vol. 81, Jan-March 2009

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Thank you for your attention
Angela.Intermite@quasar-group.org...
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