Www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Sinn für Drehungen im Nanokosmos Stefan Blügel IFF-I, Institut für Festkörperforschung.

Präsentation zum Thema: "Www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Sinn für Drehungen im Nanokosmos Stefan Blügel IFF-I, Institut für Festkörperforschung."—  Präsentation transkript:

1 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Sinn für Drehungen im Nanokosmos Stefan Blügel IFF-I, Institut für Festkörperforschung

2 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Marilyn Monroe Encore Celebrity Images

3 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Marilyn Monroe Andy Warhol

4 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Reminder : Chirality An object that cannot be superimposed on its mirror image mirror Chiral objects Nonsuperimposable mirror images mirror Nonchiral objects superimposable mirror images

5 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Chirale Moleküle

6 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Chirale Moleküle

7 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Reminder : Parity violation Parity principle: Right and left handed versions of chiral objects or processes should exist with equal probability Electro-weak interaction SU(2) L Parity violation in terrestrial Biopolymers: DNA Exceptions:

8 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Drehimpuls L = m (v x r) t  -t  v  -v  L  -L Time-inversion symmetry (1) Rechtsdrehung vorwärts Rechtsdrehung rückwärts L r v t  -t  v  -v  L  -L t  -t

9 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Time-inversion symmetry (2) Rechtsdrehung rückwärts Linksdrehung vorwärts Der zeitumgekehrte Prozess lässt sich physikalisch realisieren!

10 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Spatial inversion (parity) Der spiegelbildliche Prozess (hier ebenfalls die umgekehrte Drehung) ist ebenfalls physikalisch realisierbar. Inversion hier veranschaulicht an hand der ähnlichen Spiegelung

11 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Helizität des Lichts Die Intensität des Lichts bestimmt die Anzahl der Photonen, die wie Teilchen agieren Lichtgeschwindigkeit 50% aller Photonen haben Chiralität= -1 50% aller Photonen haben Chiralität= +1

12 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Der Photoelektrische Effekt Metalloberfläche Die Intensität des Lichts bestimmt die Anzahl der Elektronen 50% aller Elektronen haben Chiralität=-1/2 50% aller Elektronen haben Chiralität= +1/2

13 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Spiral Galaxies

14 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Parity Violation at Surfaces time inversion T mirror reflection R time inversion T mirror reflection R time inversion T E =E(TR) E E ≠E(TR) mirror reflection R

15 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Homochiral Magnetic State

16 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Consequences of symmetry breaking |L>|R> FM/AFM E(c) c For magnetic nanostructure it holds that: If chirality can be broken, spin-orbit interaction will break it! After 25 years of surface magnetism, is this of relevance or is it smoke of theory? oDoes ferro- or antiferromagnetism exists at surfaces at all ? oFor domain walls, chirality can be broken i.e. there should be only walls of one type

17 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Complete Picture Heisenberg Exchange Dzyaloshinskii Moriya-Exchange Magneto- Crystalline Anisotropy Dipol-Dipol Anisotropy

18 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Phase Diagramme M. Heide, G. Bihlmayer and S. Blügel

19 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Model system: Monolayer Mn on W(110) 0.75 ML + 100 meV/Atom ± 0 meV/Atom + 70 meV/Atom Magnetic Configuration : Pseudomorphic Growth: M. Bode et al., Surf. Sci. 432, 8 (1999). Cu-Atome Vakuum Mn-Atome

20 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Imaging Mn/W(110) Non-magnetic W-Tip S. Heinze, M. Bode et al., Science 288, 1805 (2000).

21 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Quantum Mechanics of Electrons: Many-body problem iron atom: 26 electron wave-function: Ψ(r 1,...r 26 ) store only 10 values per coordinate: 10 78 values assume each value could be stored in a single H atom: memory heavier than the milky way

22 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Density Functional Theory (DFT) Total Energy: Secular Equation: Density: Energy is functional of electron density n and external parameters such as lattice constants, atoms positions, magnetization direction… CPU time proportional to N 3 : Selfconsistency loop

23 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 The Nobel Prize in Chemistry 1998 "for his development of the density- functional theory" "for his development of computational methods in quantum chemistry" Walter KohnJohn A. Pople

24 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Revolution in Computing Power: cutting supercomputing in nanomagnetism A. E. Brenner, Physics Today, October 1996 $1K

25 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Imaging the Magnetic Ground State of 1ML-Mn/W(110) Non-magnetic W-Tip Magnetic Fe-Tip î First experimental Proof of the 2D-AFM! S.Heinze, M. Bode, A. Kubetzka, X. Nie, O. Pietsch, S.Blügel, Wiesendanger, Science 288 (2000)

26 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Revolution in Computing Power: cutting supercomputing in nanomagnetism A. E. Brenner, Physics Today, October 1996 $1K

27 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 New Interaction discovered Bode, Heide, von Bergmann, Ferriani, Heinze, Bihlmayer, Kubetzka, Pietzsch, Bl ü gel, Wiesendanger, cycloidal spiral x Nature 447, 190 (2007) |L>|R> FM/AFM E(c) c JUMP

28 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007

29 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Tool-driven revolutions Dyson, F., Imagined Worlds, Harvard University Press, Cambridge, MA, 1997, pgs. 50-51. New directions in science are launched by new tools more often than by new scientific concepts. The effect of a concept-driven revolution is to explain old things in new ways. The effect of a tool-driven re- volution is to discover new things that have to be explained. We have been more successful in dis- covering new things than in explaining old ones. The computer incidentially caused a revolution in physics itself, increasing the power of physical theories to interpret experiments and predict phenomena. The computer and the algorithms are prime example of an intellectual tool.

30 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Vision: Simulation Triangle@FZJ Research Area Simulation JSF GRS IAS NIC GAUSS PACE DEISA JARA-SIM JPSS Th. Lippert & S.Blügel

31 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Institute for Advanced Simulation (IAS) Computational Biotechnology Computational Biophysics Computational Nanoscience Quantum Computing Computational Neuroscience Computation Engineering

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34 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Markus Heide Gustav Bihlmayer Collaboration: Paolo Ferriani Stefan Heinze Matthias Bode Kirsten von Bergmann Nacho Pascual Ph. Hofmann Helmholtz Association of Research Centers (HGF) Deutsche Forschungsgemeinschaft (DFG) Sponsers:

35 www.fz-juelich.de/iff/e_th1 Bad Neuenahr June -2007 Theory-1 Group at IFF