MPI Stuttgart. Atomic-scale control of graphene magnetism using hydrogen atoms. HiMagGraphene.

Transcription

1 MPI Stuttgart Atomic-scale control of graphene magnetism using hydrogen atoms HiMagGraphene Budapest, April, 2016

2 Magnetism in graphene: just remove a p z orbital Atomic Hydrogen π σ m T = m π = 1μ B (1.0 m B ) O. Yazyev, Rep. Prog. Phys (2010)

3 Atomic Hydrogen on Monolayer Graphene DOS (au) Desorption energy (ev) Relaed Atomic structure Calculated spin density Magnetic moment = 1μ B spin density located on the opposite triangular sublattice. Simulated STM image (Tersoff-Hamann) m T = m π = 1μ B Spin Up QL (1.0 m Spin Down B ) Graphene H chemisorbs on Graphene 3 Adsorption Energy 0.9eV Distance of H atom over graphene (Å) Energy (ev) DFT calculations: M. Moaied, J.J Palacios, Feli Yndurain Spin Polarized DFT SIESTA code // (DZP) basis set.

4 Eperimental UHV-STM approach Illustration by Julio Gómez-Herrero

5 DOS (au) di/dv (a.u.) di/dv LDOS Starting point of the project! Spin-split peaks!! 20meV Atomic Hydrogen Voltage (mv) Spin Up Spin Down Graphene m T = m π = 1μ B Theoretical prediction Energy (ev)

6 di/dv (a.u.) di/dv LDOS Proposed eperiments Spin-split peaks!! 20meV Voltage (mv)

7 The consortium (who we are) Coordinator (P1) Partner 2 Partner 3 P.I. co-investigator P.I. co-investigator P.I. MPI Stuttgart co-investigator I. Brihuega J.M.Gómez-Rodríguez J-Y Veuillen P. Mallet K. Kern M.Ternes Quasiparticle pseudospin BILAYER I Brihuega, P. Mallet, C. Bena, S. Bose, C. Michaelis, L. Vitali, F. Varchon, L.Magaud, K. Kern, J.Y. Veuillen Phys Rev. Lett. 101, (2008) 2.5Å MONOLAYER 2.5Å

8 True variable Temperature eperiments 40 K T Point defects in graphene

9 Preparation of graphene substrates 4 th layer 3 rd layer 2 nd layer 1 st layer G/SiC-C doped twisted bi(tri)layer Gr 3232 nm² nm² Si C G/SiC-Si Neutral (thick) twisted multilayer ribbons on SiC samples 44 nm² Heavily doped ML and BL Gr Armchair edge 55 nm² Zig-Zag edge

10 Magnetic Field dependence Spin polatization

11 Chronogram of activities: WP1. Substrate preparation and characterization (0-36) SiC(000-1): from ML to multilayer graphene; SiC(0001): ML and BL; HOPG; ML on BN/SiO 2 ; ML on SiO 2 ; ML graphene on (Au, Cu, Ir, Pt); graphene islands and ribbons on SiC. WP2. STS Characterization of H on undoped graphene (0-36) - LDOS of single H for different substrates - Spatial etension of the spin-split state - Interaction between graphene magnetic moments induced by neighboring H atoms WP3. Temperature dependent measurements (12-36) - Influence of thermal fluctuations in the magnetic moments - Dynamic evolution of H atoms. - Single and ensembles of H atoms WP4. Magnetic field dependence (6-36) - Proof of the magnetic origin of the peaks by using spin-sensitive tips - Observing the energy shifts due to the Zeeman energy - Determine the coupling strength and sign in ensembles of H atoms WP5. Spin manipulation (6-36) - Locally: using the STM tip to manipulate the H adsorption sites - Eternally: with doping (both by substrate and by gating) - On a device: try to inject spin polarized current without magnetic electrodes. time [months]

12 Role of the partners (who does what) WP3. Temperature dependence WP1. Substrate preparation and characterization WP2. STS of H on undopped graphene WP4. Magnetic field dependence 6-36 Comprehensive characterization of H-induced graphene magnetism WP5. Spin manipulation

13 WP1: Enabling Research WP2: Spintronics

14 MPI Stuttgart HiMagGraphene Progress so far

15 Manipulating H magnetism

16 Manipulating H magnetism

17 Manipulating H magnetism 7 H atoms up 7 H atoms up 7 H atoms down 7 H atoms down

18 Manipulating H magnetism 7 H atoms up 7 H atoms up 7 H atoms down 7 H atoms down

19 Manipulating H magnetism 7 H atoms up 7 H atoms down 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, submitted

20 Manipulating H magnetism 7 H atoms up 7 H atoms down 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, submitted

21 STM Sublattice localization of the polarized peak DFT H TOPOGRAPHY

22 E [mev] STM Sublattice localization of the polarized peak DFT LDOS (au) H -50 LDOS 1.95 V di/dv ( LDOS) mapping along the profile TOPOGRAPHY atom V Voltage (mv)

23 E [mev] STM Sublattice localization of the polarized peak DFT LDOS (au) PDOS (au) H -50 LDOS 1.95 V di/dv ( LDOS) mapping along the profile TOPOGRAPHY atom atom Spin up Spin Down atom DFT V Voltage (mv) Energy (ev) 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, submitted

24 True variable Temperature eperiments 40 K 40 K T