theory of the spin-polarized stmiffbluegel/vortrag_1… · ppt file · web view · 2007-06-21the...

Bad Neuenahr June -2007

www.fz-juelich.de/iff/e_th1

Sinn für Drehungen im Nanokosmos

Stefan Blügel

IFF-I, Institut für Festkörperforschung


www.fz-juelich.de/iff/e_th1Marilyn Monroe

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Encore Celebrity Images


www.fz-juelich.de/iff/e_th1Marilyn Monroe

Andy Warhol


www.fz-juelich.de/iff/e_th1Reminder : Chirality

An object that cannot be superimposed on its mirror image

mirror

Chiral objectsNonsuperimposablemirror images

mirror

Nonchiral objectssuperimposablemirror images


www.fz-juelich.de/iff/e_th1Chirale Moleküle



Reminder : Parity violation

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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:



Drehimpuls L = m (v x r)

t -t v -v L -L

Time-inversion symmetry (1)

Rechtsdrehung vorwärts Rechtsdrehung rückwärts

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L

r

v

t -t v -v L -L

t -t



Time-inversion symmetry (2)

Rechtsdrehung rückwärtsLinksdrehung vorwärts

Der zeitumgekehrte Prozess lässt sich physikalisch realisieren!





Spatial inversion (parity)

Der spiegelbildliche Prozess (hier ebenfalls die umgekehrte Drehung) ist ebenfalls physikalisch realisierbar.


Inversion hier veranschaulicht an hand der ähnlichen Spiegelung


www.fz-juelich.de/iff/e_th1Helizität des Lichts

Die Intensität des Lichts bestimmtdie Anzahl der Photonen, die wie Teilchen agieren

Lichtgeschwindigkeit

50% aller Photonenhaben Chiralität= -1

50% aller Photonenhaben Chiralität= +1



Der Photoelektrische Effekt

Metalloberfläche

Die Intensität des Lichts bestimmtdie Anzahl der Elektronen

50% aller Elektronenhaben Chiralität=-1/2 50% aller Elektronenhaben Chiralität= +1/2



Spiral Galaxies



Parity Violation at Surfaces

time inversion

Tmirror reflection

R

time inversion

Tmirror reflection

R

time inversion

T

E =E(TR)

E =E(TR)

E ≠E(TR)

mirror reflection

R


www.fz-juelich.de/iff/e_th1Homochiral Magnetic State



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 oris it smoke of theory?

o Does ferro- or antiferromagnetism exists at surfaces at all ?o For domain walls, chirality can be broken i.e. there should be only walls of one type


www.fz-juelich.de/iff/e_th1Complete Picture

HeisenbergExchange

DzyaloshinskiiMoriya-Exchange

Magneto-CrystallineAnisotropy

Dipol-DipolAnisotropy


www.fz-juelich.de/iff/e_th1Phase Diagramme

M. Heide, G. Bihlmayer and S. Blügel



Model system: Monolayer Mn on W(110)

0.75 ML

+ 10

0 m

eV/A

tom

+ 10

0 m

eV/A

tom

± 0

meV

/Ato

m±

0 m

eV/A

tom

+ 70

meV

/Ato

m+

70 m

eV/A

tom

Magnetic Configuration: Pseudomorphic Growth:

M. Bode et al., Surf. Sci. 432, 8 (1999).

Cu-Atome

Vakuum

Mn-Atome


www.fz-juelich.de/iff/e_th1Imaging Mn/W(110)

Non-magnetic W-TipNon-magnetic W-Tip

S. Heinze, M. Bode et al.,

Science 288, 1805 (2000).



Quantum Mechanics of Electrons: Many-body problem

iron atom:

26 electron wave-function: Ψ(r1,...r26)

store only 10 values per coordinate: 1078 values

assume each value could be stored

in a single H atom: memory heavier than the milky way



Density Functional Theory (DFT)

Total Energy:

Secular Equation:

Density:

Energy is functional of electron density n and external parameterssuch as lattice constants, atoms positions, magnetization direction…

CPU time proportional to N3:

Selfconsistency loop



The Nobel Prize in Chemistry 1998

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"for his development of the density-functional theory"

"for his development of computational methods in quantum chemistry"

Walter Kohn John A. Pople



Revolution in Computing Power:

cutting supercomputing in nanomagnetism

A. E. Brenner, Physics Today, October 1996

$1K



Imaging the Magnetic Ground State of 1ML-Mn/W(110)Non-magnetic W-TipNon-magnetic W-Tip Magnetic Fe-TipMagnetic Fe-Tip

First experimental Proof of the 2D-AFM!First experimental Proof of the 2D-AFM!S.Heinze, M. Bode, A. Kubetzka, X. Nie, O. Pietsch, S.Blügel, Wiesendanger, Science 288 (2000)



Revolution in Computing Power:

cutting supercomputing in nanomagnetism

A. E. Brenner, Physics Today, October 1996

$1K



New Interaction discovered

Bode, Heide, von Bergmann, Ferriani, Heinze, Bihlmayer, Kubetzka, Pietzsch, Blügel, Wiesendanger,

cycloidal spiral

x

Nature 447, 190 (2007)

|L> |R>

FM/AFM

E(c)

c

JUMP

λ =8nm =40atoms


www.fz-juelich.de/iff/e_th1Tool-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 explainold 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. Thecomputer and the algorithms are prime example of an intellectual tool.



Vision: Simulation Triangle@FZJ

Research AreaSimulation

JSF GRS

IAS

NICGAUSS

PACE

DEISA

JARA-SIMJPSS

Th. Lippert & S.Blügel



Institute for Advanced Simulation (IAS)

• Computational Biotechnology • Computational Biophysics• Computational Nanoscience• Quantum Computing• Computational Neuroscience• Computation Engineering



22 Artikel in Science

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54 Artikel in Nature

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• 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:


www.fz-juelich.de/iff/e_th1Theory-1 Group at IFF

theory of the spin-polarized stmiffbluegel/vortrag_1… · ppt file · web view · 2007-06-21the...

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