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Iván Brihuega-Probing graphene physics at the atomic scale

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Iván Brihuega-Probing graphene physics at the atomic scale

Los días 22 y 23 de junio de 2016 organizamos en la Fundación Ramón Areces un simposio internacional sobre 'Materiales bidimensionales: explorando los límites de la física y la ingeniería'. En colaboración con el Massachusetts Institute of Technology (MIT), científicos de este prestigioso centro de investigación mostraron las propiedades únicas de materiales como el grafeno, de solo un átomo de espesor, y al mismo tiempo más resistente que el acero y mucho más ligero.

Los días 22 y 23 de junio de 2016 organizamos en la Fundación Ramón Areces un simposio internacional sobre 'Materiales bidimensionales: explorando los límites de la física y la ingeniería'. En colaboración con el Massachusetts Institute of Technology (MIT), científicos de este prestigioso centro de investigación mostraron las propiedades únicas de materiales como el grafeno, de solo un átomo de espesor, y al mismo tiempo más resistente que el acero y mucho más ligero.

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Iván Brihuega-Probing graphene physics at the atomic scale

  1. 1. Madrid, June, 2016ivan.brihuega@uam.es www.ivanbrihuega.com Nanoscience and Scanning Probe Microscopy Group Probing graphene physics at the atomic scale
  2. 2. UHV-LT-STM Scanning tunneling microscopy (STM) Probes nanoscale systems at an atomic level Resolution: Horizontal (~ 0.1Å), vertical (~ 0.01Å) Scanning tunneling spectroscopy (STS) Local electronic structure (LDOS  dI/dV ) Resolución: ~ 1meV (T= 4K) STM chamber LHe bath cryostat Preparation chamber Miguel Moreno Ugeda, PhD thesis(2011) x107 x y VBIAS sample sample tip Vb d~10Å z
  3. 3. Atomic resolution on graphene MONOLAYER BILAYER 20nm BL: Triangular “graphite” like 3Å 1-2 ML Graphene on SiC(0001) ML: “Honeycomb” pattern. 3Å
  4. 4. Vacancy on HOPG Vacancy on G/Pt(111) Divacancy Atomic Hydrogen Influence of atomic defects
  5. 5. Graphene properties on different surfaces A.J. Martínez-Galera, et al, Nano Letters 11, 3576 (2011) a new route to grow graphene on low reactivity metals Ethylene irradiation I. Brihuega et al. Phys Rev. Lett. 101, 206802 (2008) 2.5Å BILAYER MONOLAYER 2.5Å P. Mallet et al. Phys. Rev: B 086, 45444, (2012) Quasiparticle pseudospin A.J. Martínez-Galera, et al, Scientific Reports 4, 7314 (2014) Graphene nanopatterning with 2.5 nm precision Nanopatterning H. González-Herrero, et al, ACS Nano 10, 5131 (2016) Tunable transparency
  6. 6. Graphene properties on different surfaces A.J. Martínez-Galera, et al, Nano Letters 11, 3576 (2011) a new route to grow graphene on low reactivity metals Ethylene irradiation I. Brihuega et al. Phys Rev. Lett. 101, 206802 (2008) BILAYER MONOLAYER P. Mallet et al. Phys. Rev: B 086, 45444, (2012) Quasiparticle pseudospin A.J. Martínez-Galera, et al, Scientific Reports 4, 7314 (2014) Graphene nanopatterning with 2.5 nm precision Nanopatterning H. González-Herrero, et al,) Tunable transparency Rotating two graphene layers I. Brihuega, et al. Phys. Rev. Lett. 109, 196802 (2012)
  7. 7. -1,0 -0,8 -0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 Energy(eV) Monolayer ED Γ ΓKM DFT calculations: Félix Yndurain Monolayer Rotating two graphene layers: electronic decoupling
  8. 8. Bilayer Monolayer -1,0 -0,8 -0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 Energy(eV) Monolayer Bilayer AB Γ ΓKM Rotating two graphene layers: electronic decoupling ED DFT calculations: Félix Yndurain
  9. 9. -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 Energy(eV) Monolayer Bilayer AB Rotated Bilayer Rotational disorder: Electronic decoupling (for large enough angles)Bilayer Monolayer Layers rotated 28º M. Sprinkle et al. PRL 103, 226803 (2009) Nearly ideal graphene band structure ED  EF Rotating two graphene layers: electronic decoupling ED DFT calculations: Félix Yndurain Γ ΓKM q = 28º G/SiC(000-1) … 1st layer 2nd layer 3rd layer C Si 4th layer
  10. 10. 0 5 10 15 20 25 30 0 2 4 6 8 10 12 14 MoiréPeriod(nm) q deg) Moiré pattern hypothesis P=a/2*sin(q/2) Rotating two graphene layers: geometry Generation of Moiré Patterns: Periodic potential!
  11. 11. 0 5 10 15 20 25 30 0,0 0,2 0,4 0,6 0,8 1,0 vF (q)/v 0 F Rotation angle q (°) Fermi velocity Renormalization Rotating two graphene layers : tunning Fermi velocity JMB Lopes dos Santos et al, Phys. Rev Lett. 99, 256802 (2007) G. Trambly de Laissardière et al. Nano Letters 10, 804 (2010) R. Bistritzer et al. PNAS 108, 12233 (2011) ... 60 45 4055 50 35 30 Rotation angle q(º)
  12. 12. KK q DEvHs DOS  K q KK K’K’ K’K’ K’K’ vF(q)/v0 F 0 105 q (degrees) 01 10 3 1.4 Moiré period (nm) Rotating two graphene layers: Van Hove Singularities Emergence of Van Hove Singularities Reciprocal space K
  13. 13. K K q= 9.6º DEvHs DOS  K K q K K K’ K’ K’K’ K’ K’ vF(q)/v0 F 0 105 q (degrees) 01 10 3 1.4 Moiré period (nm) Rotating two graphene layers: Van Hove Singularities Emergence of Van Hove Singularities Reciprocal space
  14. 14. SiC(000-1) experimental sample: many rotational domains Image size: 320x320nm2Moiré period= 4.0 nm (q=3.6°) 1nm Moiré period= 2.4 nm (q=5.9°) 1nm P=a/2*sin(q/2)
  15. 15. q = 9.6°5 nm q = 9.6° 5 nm 0 2 4 6 8 10 0,0 0,5 1,0 1,5 2,0 VHsseparation(eV) Rotation angle q (°) 3.514 7 2.4 1.7 1.4 Moiré size -1,2 -0,8 -0,4 0,0 0,4 0,8 1,2 0,0 0,2 0,4 0,6 0,8 1,0 .4°(max) 1.4°(min) 3.5° 6.4° 9.6° dI/dV(au) Sample bias (V) Rotating two graphene layers: Robust Van Hove Singularities Graphene layers on SiC(000-1) T=6 K
  16. 16. q = 9.6° q = 6.4°5 nm 5 nm q = 6.4° 5 nm 0 2 4 6 8 10 0,0 0,5 1,0 1,5 2,0 VHsseparation(eV) Rotation angle q (°) 3.514 7 2.4 1.7 1.4 Moiré size -1,2 -0,8 -0,4 0,0 0,4 0,8 1,2 0,0 0,2 0,4 0,6 0,8 1,0 1.4°(max) 1.4°(min) 3.5° 6.4° 9.6° dI/dV(au) Sample bias (V) Rotating two graphene layers: Robust Van Hove Singularities Graphene layers on SiC(000-1) T=6 K
  17. 17. q = 9.6° q = 6.4° q = 3.5°5 nm 5 nm 5 nm q = 3.5° 5 nm -1,2 -0,8 -0,4 0,0 0,4 0,8 1,2 0,0 0,2 0,4 0,6 0,8 1,0 1.4°(max) 1.4°(min) 3.5° 6.4° 9.6° dI/dV(au) Sample bias (V) 0 2 4 6 8 10 0,0 0,5 1,0 1,5 2,0 VHsseparation(eV) Rotation angle q (°) 3.514 7 2.4 1.7 1.4 Moiré size Rotating two graphene layers: Robust Van Hove Singularities Graphene layers on SiC(000-1) T=6 K
  18. 18. q = 1.4° 5 nm q = 1.4° 5 nm -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.4°(max) 1.4°(min) 3.5° 6.4° 9.6° dI/dV(au) Sample bias (V) 0 2 4 6 8 10 0,0 0,5 1,0 1,5 2,0 VHsseparation(eV) Rotation angle q (°) 3.514 7 2.4 1.7 1.4 Moiré size Rotating two graphene layers: Robust van Hove Singularities q = 9.6° q = 6.4° q = 3.5°5 nm 5 nm 5 nm Graphene layers on SiC(000-1) T=6 K
  19. 19. 5 nm 0 2 4 6 8 10 0,0 0,5 1,0 1,5 2,0 VHsseparation(eV) Rotation angle q (°) 3.514 7 2.4 1.7 1.4 Moiré size -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.4°(max) 1.4°(min) 3.5° 6.4° 9.6° dI/dV(au) Sample bias (V) q1-10° Rotating two graphene layers: Robust van Hove Singularities q = 1.4° 5 nm q = 9.6° q = 6.4° q = 3.5°5 nm 5 nm 5 nm Graphene layers on SiC(000-1) T=6 K
  20. 20. DEVHs=2ħ·vF·K·sin(q/2)-2tq K=1.703 Å-1 - Strength of the interlayer interaction => - Fermi velocity of a graphene monolayer => JMB Lopes dos Santos et al, Phys. Rev Lett. 99, 256802 (2007) DEVHs=2ħ·vF·K·sin(q/2)-2tq K=1.703 Å-1 - Strength of the interlayer interaction => tq = 0.108 eV - Fermi velocity of a graphene monolayer => vF =1.12 106m/s JMB Lopes dos Santos et al, Phys. Rev Lett. 99, 256802 (2007) I. Brihuega, P. Mallet, H. González-Herrero, G. Trambly de Laissardière, MM. Ugeda, L. Magaud, JM. Gómez-Rodríguez, F. Ynduráin, JY. Veuillen. Phys. Rev. Lett. 109, 196802 (2012) -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.4°(max) 1.4°(min) 3.5° 6.4° 9.6° dI/dV(au) Sample bias (V) Rotating two graphene layers : Robust van Hove Singularities 5 nm q1-10° 0 2 4 6 8 10 0,0 0,5 1,0 1,5 2,0 VHsseparation(eV) Rotation angle q (°) 3.514 7 2.4 1.7 1.4 Moiré size
  21. 21. Graphene Nanopatterning with 2.5 nm precision Cluster superlattice on graphene/Ir(111) moire 250 x 250 nm2 N'Diaye et al. Phys. Rev. Lett. 97, 215501 (2006).
  22. 22. Graphene Nanopatterning with 2.5 nm precision A.J. Martínez-Galera, I. Brihuega, A. Gutiérrez-Rubio, T. Stauber, J. M. Gómez-Rodríguez, Scientific Reports 4, 7314 (2014 1 2 3 0 5000 10000 15000 20000 Numberofcounts Conductance (2e 2 /h) 0.0 0.5 1.0 0 1 2 G(2e 2 /h) Z (nm) Forward Backward +0.1V +1.0V +2.2V 2.2V +3.0V 3.0V 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.0 0.2 0.4 0.6 0.8 1.0 ExtractionProbability Z (nm)
  23. 23. Graphene Nanopatterning with 2.5 nm precision A.J. Martínez-Galera, I. Brihuega, A. Gutiérrez-Rubio, T. Stauber, J. M. Gómez-Rodríguez, Scientific Reports 4, 7314 (2014) 1 2 3 0 5000 10000 15000 20000 Numberofcounts Conductance (2e 2 /h) 0.0 0.5 1.0 0 1 2 G(2e 2 /h) Z (nm) Forward Backward +0.1V +1.0V +2.2V 2.2V +3.0V 3.0V 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.0 0.2 0.4 0.6 0.8 1.0 ExtractionProbability Z (nm) Ir clusters W clusters
  24. 24. Point defects as a source of graphene magnetism Vacancy on HOPG Vacancy on G/Pt(111) Divacancy Atomic Hydrogen
  25. 25. Point defects as a source of graphene magnetism Vacancy on HOPG Vacancy on G/Pt(111) Divacancy Atomic Hydrogen
  26. 26. Magnetism in graphene: just remove a pz orbital Atomic Hydrogen mT = mπ = 1μB (1.0 mB) π σ O. Yazyev, Rep. Prog. Phys. 73 056501 (2010) 2D honeycomb lattice of carbon atoms 2.46Å Wave vector How can we make graphene magnetic?
  27. 27. Atomic Hydrogen on Monolayer Graphene Relaxed Atomic structure Calculated spin density • Magnetic moment = 1μB • spin density located on the opposite triangular sublattice. DFT calculations: M. Moaied, J.J Palacios, Felix Yndurain •Spin Polarized – DFT SIESTA code // (DZP) basis set. 0 1 2 3 4 5 -1 0 1 2 3 Desorptionenergy(eV) Distance of H atom over graphene (Å) Adsorption Energy  0.9eV H chemisorbs on Graphene -0.4 -0.2 0.0 0.2 0.4 DOS(au) Energy (eV) Spin Up Spin Down Graphene mT = mπ = 1μB (1.0 mB)QL Simulated STM image (Tersoff-Hamann)
  28. 28. Illustration by Julio Gómez-Herrero Experimental approach UHV-4K-STM M. M. Ugeda, Doctoral Thesis, 2011.
  29. 29. Atomic Hydrogen on G/SiC(000-1) Rotational disorder: Electronic decoupling (for large enough angles) Last graphene layer is basically decoupled with ED~EF
  30. 30. -100 -50 0 50 100 0 dI/dV(a.u.) Voltage (mV) dI/dV∝LDOS -200 -100 0 100 200 1 H atom Graphene dI/dV(a.u.) Voltage (mV) H on G/SiC(000-1) – STS experiments Spin-split peaks!! -0.4 -0.2 0.0 0.2 0.4 DOS(au) Energy (eV) Spin Up Spin Down Graphene Atomic Hydrogen mT = mπ = 1μB  20meV
  31. 31. -100 dI/dV(a.u.) Experiment U3 ψ2 ) ) Coulomb splitting r1 U1 U2r2 r3 A B C H on G/SiC(000-1) – Origin of the spin-split state -0.4 -0.2 0.0 0.2 0.4 DOS(au) Energy (eV) Spin Up Spin Down Graphene Atomic Hydrogen -100 -50 0 50 100 0 dI/dV(a.u.) Voltage (mV) dI/dV∝LDOS  20meV Experiment
  32. 32. -100 dI/dV(a.u.) Experiment U3 ψ2 ) ) Coulomb splitting r1 U1 U2r2 r3 A B C -100 dI/dV(a.u.) Experiment U3 ψ2 ) ) Coulomb splitting r1 U1 U2r2 r3 A B C H on G/SiC(000-1) – Origin of the spin-split state -0.4 -0.2 0.0 0.2 0.4 DOS(au) Energy (eV) Spin Up Spin Down Graphene Atomic Hydrogen -100 -50 0 50 100 0 dI/dV(a.u.) Voltage (mV) dI/dV∝LDOS  20meV Experiment U n↑=1; n=0 20 meV splitting => We expect an extended magnetic state
  33. 33. Sublattice localization of the polarized peak TOPOGRAPHY DFT STM H
  34. 34. -100 -50 0 50 100 LDOS(au) Voltage (mV)  atom Sublattice localization of the polarized peak TOPOGRAPHY DFT STM +50 0 -50 E[meV] 1.95 V -0.88 V LDOS dI/dV (∝ LDOS) mapping along the profile H
  35. 35. -100 -50 0 50 100 LDOS(au) Voltage (mV)  atom -100 -50 0 50 100 LDOS(au) Voltage (mV)  atom  atom +50 0 -50 E[meV] 1.95 V -0.88 V LDOS dI/dV (∝ LDOS) mapping along the profile -0.4 -0.2 0.0 0.2 0.4 0 PDOS(au) Energy (eV) Spin up Spin Down Sublattice localization of the polarized peak TOPOGRAPHY DFT STM H DFT  atom H Peak height  magnetic moment
  36. 36. +50 0 E[meV] 1.95 V -0.88 V LDOS -50 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic Same sublattice 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic AB-Non-magnetic Same sublattice Different sublattice Sublattice localization of the polarized peak H Non-magnetic Ferro Magnetic coupling in graphene sensitive to where magnetic moments are located in lattice HH 2.5 3.50 Distance to H [nm]
  37. 37. Manipulating H magnetism H. González-Herrero, J. M. Gómez-Rodríguez, P. Mallet, M. Moaied, J. J. Palacios, C. Salgado, M.M. Ugeda, J. Y. Veuillen, F. Ynduráin and I. Brihuega, Science, 352, 437 (2016)
  38. 38. Manipulating H magnetism H. González-Herrero, J. M. Gómez-Rodríguez, P. Mallet, M. Moaied, J. J. Palacios, C. Salgado, M.M. Ugeda, J. Y. Veuillen, F. Ynduráin and I. Brihuega, Science, 352, 437 (2016)
  39. 39. Manipulating H magnetism 7 H atoms “down” 7 H atoms “up” 7 H atoms “up” 7 H atoms “down” H. González-Herrero, J. M. Gómez-Rodríguez, P. Mallet, M. Moaied, J. J. Palacios, C. Salgado, M.M. Ugeda, J. Y. Veuillen, F. Ynduráin and I. Brihuega, Science, 352, 437 (2016)
  40. 40. Manipulating H magnetism 7 H atoms “down” 7 H atoms “up” 7 H atoms “up” 7 H atoms “down” x x xx xx x H. González-Herrero, J. M. Gómez-Rodríguez, P. Mallet, M. Moaied, J. J. Palacios, C. Salgado, M.M. Ugeda, J. Y. Veuillen, F. Ynduráin and I. Brihuega, Science, 352, 437 (2016)
  41. 41. Manipulating H magnetism 7 H atoms “down” 7 H atoms “up” x x xx xx x 7 H atoms “down” H. González-Herrero, J. M. Gómez-Rodríguez, P. Mallet, M. Moaied, J. J. Palacios, C. Salgado, M.M. Ugeda, J. Y. Veuillen, F. Ynduráin and I. Brihuega, Science, 352, 437 (2016)
  42. 42. Manipulating H magnetism 7 H atoms “up” … 7 H atoms “down” 7 H atoms “up” x x xx xx x 7 H atoms “down” H. González-Herrero, J. M. Gómez-Rodríguez, P. Mallet, M. Moaied, J. J. Palacios, C. Salgado, M.M. Ugeda, J. Y. Veuillen, F. Ynduráin and I. Brihuega, Science, 352, 437 (2016) https://www.youtube.com/watch?v=NmPAAo7_xY0
  43. 43. J.M.Gómez-Rodríguez …and the most important slide Félix Ynduráin Paco Guinea H. González-Herrero Juanjo Palacios M. Moaied www.ivanbrihuega.com C. Salgado M. M. Ugeda J-Y VeuillenP. MalletL. Magaud Guy Trambly de Laissardière
  44. 44. Atomic H on Doped graphene -0.4 -0.2 DOS(au) Ene -100 -50 0 50 100 dI/dV(a.u.) Voltage (mV) Experiment Theory Spin up Spin down Graphene H atom Graphene ~20 meV U3 ψ2 ) ) Coulomb splitting r1 U1 U2r2 r3 A B C D E Anderson Impurity model P. W. Anderson, Physical Review 124, 41 (1961) -100 -50 0 50 100 dI/dV(a.u.) Voltage (mV) 2D E↑ E MAGNETIC NON-MAGNETIC pD/U x=(EF-Ed)/U 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 E↑=Ed+U(n  1/2) E =Ed+U(n↑  1/2) STS on neutral graphene
  45. 45. Atomic H on Doped graphene -0.4 -0.2 DOS(au) Ene -100 -50 0 50 100 dI/dV(a.u.) Voltage (mV) Experiment Theory Spin up Spin down Graphene H atom Graphene ~20 meV U3 ψ2 ) ) Coulomb splitting r1 U1 U2r2 r3 A B C D E Anderson Impurity model P. W. Anderson, Physical Review 124, 41 (1961) -100 -50 0 50 100 dI/dV(a.u.) Voltage (mV) 2D E↑ E MAGNETIC NON-MAGNETIC pD/U x=(EF-Ed)/U 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 E↑=Ed+U(n  1/2) E =Ed+U(n↑  1/2)
  46. 46. Peak splitting vs unit cell size 0.00 0.02 0.04 0.06 0.08 0.00 0.05 0.10 0.15 0.20 Splitting[eV] 1/Distance (Å -1 ) 50 25 17 12.5 Distance (Å) Fit to1/r Unit cell size matters!
  47. 47. -50 0 50 0 2 4 dI/dV(a.u.) Voltage (mV) 2 isolated H atoms on the same terrace, same tip e-h symmetry 2 isolated H atoms on the same terrace, 1 isolated H atom dif terrace small local doping,same tip 1 isolated H atom dif terrace dif tip -50 0 50 0 2 4 dI/dV(a.u.) Voltage (mV)
  48. 48. -0,2 0,0 0,2 DOS(au) Spin Down Monolayer Spin Down BL Moire (13º) Spin Down AB Bilayer(on ) Spin Down AB Bilayer(on ) Spin Up ML Spin Up BL Moire (13º) Spin Up AB Bilayer(on ) Spin Up AB Bilayer(on ) 0 25 50 75 100 125 AB Bilayer(on ) AB Bilayer(on ) BL Moire (13º) Monolayer Spinsplitting(meV) 4.4nm 4.4nm A B Influence of stacking -40 -20 0 20 40 2 4 A B dI/dV(a.u.) Voltage (mV)
  49. 49. H on HOPG – Is magnetism preserved? System is still magnetic in multilayer graphene/graphite DFT calculations: M. Moaied and J.J Palacios Bilayer Multilayer
  50. 50. -0.5 +0.50.0 E (eV) -0.5 +0.50.0 E (eV) -0.5 +0.50.0 E (eV) -0.5 +0.50.0 E (eV)-60 -40 -20 0 20 40 60 0,5 1,0 1,5 AA dimer (3nm) dI/dV(a.u.) Voltage (mV) 4.5nm -60 -40 -20 0 20 40 60 0.5 1.0 1.5 Single H AA dimer dI/dV(a.u.) Voltage (mV) H-H distance=0.5nm H-H distance=3nm
  51. 51. -60 -40 -20 0 20 40 60 0,5 1,0 1,5 Single H AA dimer0.5nm AA dimer (3nm) dI/dV(a.u.) Voltage (mV) 4.5nm H-H distance=0.5nm H-H distance=3nm -60 -40 -20 0 20 40 60 0.5 1.0 1.5 Single H AA dimer dI/dV(a.u.) Voltage (mV)
  52. 52. -300 -200 -100 0 100 200 300 0 2 dI/dV(a.u.) Voltage (mV) Atomic H on Doped graphene H atoms on 3rd graphene layer ED kF=0.020nm-1=> ED  -0.14eV 4 3rd graphene layer on SiC(000-1) is n-doped: K1 E kx ky ED K1 E kx ky EF =ED Free-standing graphene EF 2kF -400 -200 0 200 dI/dV(a.u.) Voltage (mV) ED  -0.14eV G/SiC(000-1) SiC C 1st layer 2nd layer 3rd layer DFT calculations: F Yndurain 0.8e - 1.0e - 0.9e - 0.1e - Spin Up Spin Down Non-Magnetic 0.7e - 0.5e - 0.3e - 0.2e - 0.4e - 0.6e - 0.0 0.5 1.0 0.0 0.2 0.4 0.6 0.8 1.0
  53. 53. -0.6 -0.4 -0.2 0.0 0.2 0.4 Non doped Doped with 1e - Energy (eV) DOS(au) -0.1 0.0 0.1 0.8e - 0e - 1.0e - 0.9e - 0.1e - DOS(au) Energy (eV) Spin Up Spin Down Non-Magnetic 0.7e - 0.5e - 0.3e - 0.2e - 0.4e - 0.6e - -0.5 0.0 0.5 DOS(au) Energy (eV) AB dimer Graphene Theory H-H distance=1.15nm -400 -200 0 200 400 AB Dimer Graphene dI/dV(a.u.) Voltage (mV) -50 0 50 0 2 4 dI/dV(a.u.) Voltage (mV) Atomic H on Doped graphene -400 -300 -200 -100 0 100 200 300 400 0.0 0.2 0.4 0.6 0.8 1.0 1.2 dI/dV(a.u.) Voltage (mV) -200 -100 0 100 200 0,0 0,2 0,4 0,6 0,8 1,0 dI/dV(a.u.) Voltage (mV) Single H atom Non-Magnetic Dimer STM
  54. 54. Kondo… “This problem has to be solved properly…” Misha Katsnelson, ICMM, Madrid, 19.09.2014
  55. 55. 0 1 2 3 4 5 0 1 2 3 Desorptionenergy(eV) Distance of H atom over graphene () Single H Atomic H deposition on SiC(000-1) held at RT + 6 minutes at RT => Cool down to 6K Atomic H on G/SiC(000-1) -100 -50 0 50 100 0 2 dI/dV(a.u.) Voltage (mV) x
  56. 56. -100 -50 0 50 100 0 2 dI/dV(a.u.) Voltage (mV) 0 1 2 3 4 5 0 1 2 3 Desorptionenergy(eV) Distance of H atom over graphene () Single H Atomic H deposition on SiC(000-1) held at RT + 6 minutes at RT => Cool down to 6K Atomic H on G/SiC(000-1) -100 -50 0 50 100 0 1 2 dI/dV(a.u.) Voltage (mV) x x
  57. 57. 1175.top 1178.top 1184.top 1187.top Manipulating H magnetism -200 -100 0 100 200 0.0 0.5 1.0 1.5 2.0 dI/dV(a.u.) Voltage (mV) -200 -100 0 100 200 0.0 0.5 1.0 1.5 2.0 dI/dV(a.u.) Voltage (mV) H_SiC(000-1)_2013_06_17_RT_HDeposition
  58. 58. -0.10 -0.05 0.00 0.05 0.10 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 E-EF (eV) k (Å -1 ) -0.10 -0.05 0.00 0.05 0.10 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 E-EF (eV) k (Å -1 ) 1 2 3 0 5000 10000 15000 20000 Numberofcounts Conductance (2e 2 /h) 0.0 0.5 1.0 0 1 2 G(2e 2 /h) Z (nm) Forward Backward +0.1V +1.0V +2.2V 2.2V +3.0V 3.0V 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.0 0.2 0.4 0.6 0.8 1.0 ExtractionProbability Z (nm)a) b) c) d) e) f) g) h) i) j) k) l) m) Graphene Nanolithography with 2.5 nm precision A.J. Martínez-Galera, I. Brihuega, A. Gutiérrez-Rubio, T. Stauber, J. M. Gómez-Rodríguez
  59. 59. Tunneling on and through graphene: measuring the local electronic coupling. BothCu(111)&Graphenecanbeobserved Same region as above, tip change G/Cu(111)vsCu(111) Dispersion relation Pseudospin -0,8 -0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 -0,4 -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 k (nm -1 ) Energy(eV) G/Pt(111)G/SiC(000-1) Gr/Cu(111) vF = 1.12x106 m/s ED = -0.34 eV kF = 0.48 eV FT from G/Cu(111) Point defects Grapheneproperties H. González-Herrero, A.J. Martínez-Galera, M.M. Ugeda, F.Craes, D. Fernández-Torre, P. Pou, R. Pérez, J.M. Gómez-Rodríguez and I. Brihuega
  60. 60. 1175.top 1171.top x 1179.top x 1178.top 1184.top 1173.top x 1187.top 1191.top Manipulating H magnetism H dimer in same sublattice => H dimer in opposite sublattice=> Remove the dimer Spin polarized peak No peaks at low E H dimer in opposite sublattice => Remove 1 H atom from dim No peaks at low E Spin polarized peak x
  61. 61. 0 0.2 0.4 0.6 -0.8 -0.4 0 0.4 0.8 Bottom Top dI/dV(arb.units) Sample bias (V) 0 0.1 0.2 0.3 -1 -0.5 0 0.5 1 dI/dV(arb.units) Sample bias (V) 0 0.2 0.4 0.6 -0.2 -0.1 0 0.1 0.2 1 1' 2 3 dI/dV(arb.units) Sample bias (V) 1 1’ 2 3 0 2 4 6 8 10 0.0 0.5 1.0 1.5 2.0 VHsseparation(eV) Rotation angle q (°) 3.514 7 2.4 1.7 1.4 Moiré size Rotating two graphene layers: only upmost 2 layers matter Left Right I. Brihuega, P. Mallet, H. González-Herrero, G. Trambly de Laissardière, MM. Ugeda, L. Magaud, JM. Gómez-Rodríguez, F. Ynduráin, and J-Y. Veuillen to appear
  62. 62. 1.65 V 0.05 V LDOS High Low Moiré period 2.66nm (q  5.30°).
  63. 63. Moiré period  11-12nm; q  1.3º-1.2º
  64. 64. 0.20.10-0.1-0.2 0.5 0.4 0.3 0.2 0.1 Bias [V] CH6[V] 0.10-0.1 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 Bias [V] CH6[V] Moiré period  11-12nm; q  1.3º-1.2º 2001000-100-200 300 250 200 150 100 50 0 X[mV] Z[mV] Average AA Average AB
  65. 65. H “dimers” on G/SiC(000-1) H-H distance=0.28nm AB dimer H-H distance=0.49nm AA dimer 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic AB-Non-magnetic Same sublattice Different sublattice Experiment STS -200 0 200 1 dI/dV(a.u.) Voltage (mV) Graphene Theory (DFT)
  66. 66. STS -200 0 200 1 dI/dV(a.u.) Voltage (mV) Graphene H “dimers” on G/SiC(000-1) 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic AB-Non-magnetic Same sublattice Different sublattice Graphene STS -200 0 200 1 dI/dV(a.u.) Voltage (mV) AB dimer -0.5 0.0 0.5 AB Dimer Graphene DOS(au) Energy (eV) DFT H-H distance=0.28nm AB dimer H-H distance=0.49nm AA dimer Experiment Theory (DFT)
  67. 67. -200 0 200 1 dI/dV(a.u.) Voltage (mV) STS AA dimer STS -200 0 200 1 dI/dV(a.u.) Voltage (mV) AB dimer H “dimers” on G/SiC(000-1) 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic AB-Non-magnetic Same sublattice Different sublattice -0.5 0.0 0.5 AB Dimer Graphene DOS(au) Energy (eV) DFT Graphene AB dimer H-H distance=0.28nm AB dimer H-H distance=0.49nm AA dimer Experiment Theory (DFT) AA Dimer Spin up Spin down -0.5 0.0 0.5 AB Dimer Graphene DOS(au) Energy (eV) DFT
  68. 68. -200 0 200 1 dI/dV(a.u.) Voltage (mV) STS AA dimer STS -200 0 200 1 dI/dV(a.u.) Voltage (mV) AB dimer H “dimers” on G/SiC(000-1) 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic AB-Non-magnetic Same sublattice Different sublattice -0.5 0.0 0.5 AB Dimer Graphene DOS(au) Energy (eV) DFT Graphene AB dimer H-H distance=0.28nm AB dimer H-H distance=0.49nm AA dimer Experiment Theory (DFT) AA Dimer Spin up Spin down -0.5 0.0 0.5 AB Dimer Graphene DOS(au) Energy (eV) DFT H-H distance=0.57nm AB dimer -200 -100 0 100 200 1 2 dI/dV(a.u.) Voltage (mV) STS Same sublattice => peak is polarized Different sublattices => no peaks AB dimer Graphene
  69. 69. -200 -100 0 100 200 0.5 1.0 1.5 2.0 Voltage (mV) dI/dV(a.u.) Manipulating H magnetism A-B dimer “Magnetism OFF”X X Removing single H
  70. 70. -200 -100 0 100 200 0.5 1.0 1.5 2.0 Voltage (mV) dI/dV(a.u.) Manipulating H magnetism Isolated H “Magnetism ON” Removing single H
  71. 71. -200 -100 0 100 200 0.5 1.0 1.5 2.0 dI/dV(a.u.) Voltage (mV) Manipulating H magnetism A-A dimer “Magnetism ON” Lateral motion
  72. 72. Manipulating H magnetism A-B dimer “Magnetism OFF” -200 -100 0 100 200 0.5 1.0 1.5 2.0 dI/dV(a.u.) Voltage (mV) Lateral motion
  73. 73. A-B dimer at 1.15 nm “Magnetism OFF!” x Manipulating H magnetism H-H distance=1.15nm x 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic AB-Non-magnetic Same sublattice Different sublattice -400 -200 0 200 400 AB Dimer Graphene dI/dV(a.u.) Voltage (mV) -0.5 0.0 0.5 DOS(au) Energy (eV) AB dimer Graphene Theory (DFT) A-B dimer
  74. 74. Manipulating H magnetism 0 5 10 15 -2.8 -2.4 -2.0 -1.6 Energy[ev] H-H distance [Å] AA-Ferromagnetic AB-Non-magnetic Same sublattice Different sublattice -400 -200 0 200 400 AB Dimer Graphene dI/dV(a.u.) Voltage (mV) -0.5 0.0 0.5 DOS(au) Energy (eV) AB dimer Graphene Theory (DFT) Isolated H “Magnetism ON” Exchange energy for 2H at 1.5 nm is -35meV Eex = [(2H in AA with spin 2)-(2H in AA forced to spin 0)] Isolated H

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