Magic triangle
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Transcript of Magic triangle
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Magic triangleMagic triangle
Materials science
epitaxy, self organized growth
organic synthesis
implantation, isotope purification
atom and molecule manipulation
nanolithography, nanoprinting
beam and scanning probes
....
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Magic triangleMagic triangle
Materials science
epitaxy, self organized growth
organic synthesis
implantation, isotope purification
atom and molecule manipulation
nanolithography, nanoprinting
beam and scanning probes
....
Physics of complex systems
exotic ground states and
quasiparticles phase and statistical
transformations complex dynamics
….
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Magic triangleMagic triangle
Materials science
epitaxy, self organized growth
organic synthesis
implantation, isotope purification
atom and molecule manipulation
nanolithography, nanoprinting
beam and scanning probes
....
Physics of complex systems
exotic ground states and
quasiparticles phase and statistical
transformations complex dynamics
….
High tech/IT
photonics (optoelectronics) MEMS, NEMS electronics, magnetoelectronics spintronics ….
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SEMICONDUCTOR SPINTRONICSSEMICONDUCTOR SPINTRONICS
Tomasz DIETLInstitute of Physics, Polish Academy of Sciences, Warsaw
1. Why spin electronics? -- semiconductors -- ferromagnetic metals
2. Ferromagnetic semiconductors 3. Spin manipulation -- magnetization -- single spins reviews: listed in the abstract
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Integrated circuitsIntegrated circuits
4 transistors 109 transistors processing and dynamic storage of information ; P i DRAM
20022002
J. S. Kilby
US Patent Office, 3 052 822
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Field effect transistor Si-MOS-FET
Field effect transistor Si-MOS-FET
gate
source drain
MOSFET – resistor + capacitor
Two states: conducting/non-conducting
eg. multiplication (AND)
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source, Alsource, Al
drain, Aldrain, Al
glasssubstrate
glasssubstrate
gate Al foil
gate Al foil
„semiconductor” Cu2S
„semiconductor” Cu2S
US Patent Office, 1 745 175 MES FET
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Julius Edgar Lilienfeld (1882-1963)Julius Edgar Lilienfeld (1882-1963)
Born in 1882 and till 1899 in Lvov Study and PhD (1905) in BerlinProfessor in Leipzig (1910-26) Since 1926 in USA
Kleint, Prog. Surf. Sci. ‘98
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Storing of information on hard diskStoring of information on hard disk
• high density and non-volatile (5GB/cm2 )• slow access and non-reliable (moving parts)
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Storing of information on magnetooptical disc
Storing of information on magnetooptical disc
H < HcH < Hc
T > TCT > TC
• writing: heating above TC
• reading: Kerr effect
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BarriersBarriers
• financial, legal, psychological, ...• technical - heat release, defects in oxide, ....
• physical - grain structure of matter: Coulomb blockade, ... - quantum phenomena: interference, tunneling, ... - thermodynamic phenomena: superparamagnetism, ...
• entertainment industry
• …
Driving forcesDriving forces
nanotechnology
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• New information carrier - electron photon, flux (SQUID loops), vortex (type II superconductors); - spin rather than charge ...
• New principle of device operation quantum devices, spin transistors, ...
• New architecture - physical, chemical and biological processes - quantum computing
• Integration of functions, not only elements
=> Spintronics
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SPINTRONICS exploiting spin, not only charge SPINTRONICS exploiting spin, not only charge
rational: spin robust to external perturbations
• Storing and processing of classical information
• Storing and processing of quantum information
• Sensing magnetic field
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Giant magnetoresistance (GMR) in ferromagnetic metal multilayersGiant magnetoresistance (GMR)
in ferromagnetic metal multilayers
A. Fert et al., P. Gruenberg et al., S. Parkin et al., 1988-91J. Barnaś et al. (theory)
4.2 K
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Information readingInformation reading
GMR/TMR sensors
IBM 1997-
GMR/TMR sensors
IBM 1997- GMR
TMR
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Magnetic random access memory (MRAM)
Magnetic random access memory (MRAM)
Infineon, Motorola, 256 kb
• non-volatile• fast (50 ns)• reliable• radiation hardness• ....
Difficulties:• thin oxide, 1.2 nm• large writing currents• ...
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Why to do not combine complementary properties and functionalities of semiconductor and magnetic material systems?
• hybrid structures -- overlayers or inclusions of ferromagnetic metals
=> source of stray fields and spin-polarized carriers
-- soft ferromagnets => local field amplifiers
-- hard ferromagnets => local field generators (cf. J. Kossut, ILC, Budapest’02)
• ferromagnetic semiconductors
Spintronics – material aspectsSpintronics – material aspects
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• magnetic semiconductors short-range ferromagnetic super- or double exchange
EuS, ZnCr2Se4, La1-xSrxMnO3, ... • diluted magnetic semiconductors long-range hole-mediated ferromagnetic exchange
IV-VI: p-Pb1-x-yMnxSnyTe (Story et al.’86)
III-V: In1-x-MnxAs (Munekata et al.’89,’92)
Ga1-x-MnxAs (Ohno et al.’96) TC 100 K for x = 0.05
II-VI: Cd1-xMnxTe/Cd1-x-yZnxMgyTe:N QW (Cibert et al.’97, Kossacki et al.’99)
Zn1-xMnxTe:N (Ferrand et al.’99) Be1-xMnxTe:N (Hansen et al.’01)
Ferromagnetic semiconductorsFerromagnetic semiconductors
III-V and II-VI DMS:quantum nanostructures and ferromagnetism combine
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Spin injection in p-i-n(Ga,MnMn)As /(In,Ga)As/GaAs diode (spin-LED)
Spin injection in p-i-n(Ga,MnMn)As /(In,Ga)As/GaAs diode (spin-LED)
Ohno et al., Nature ‘99
Po
lari
zati
on
(%
)
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The nature of the Mn state and its coupling to carriers
The nature of the Mn state and its coupling to carriers
Mn: 3d54s2
II-VI: Mn electrically neutral (3d5, S = 5/2) –doping by acceptors necessary
III-V: Mn acts as source of spins and holes
• large p-d hybridization and large intra-site Hubbard U =>
Kondo hamiltonian H = -NoSs => large Mn-hole exchange
-- (Ga,Mn)As: No - 1.2 eV (Szczytko et al., Okabayashi et al.)
-- (Zn,Mn)Te: No - 1.0 eV (Twardowski et al.)
• no s-d hybridization => small Mn-electron exchange
No 0.2 eV (Gaj et al.)
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Mean-field Zener modelMean-field Zener model
Which form of Mn magnetization minimizes F[M(r)]?
F = FMn [M(r)] + Fholes [M(r)]
M(r) 0 for H= 0 at T < TC
if M(r) uniform => ferromagnetic order
otherwise => modulated magnetic structure
nholes << Nspins Zener RKKY
k
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Curie temperature in p-Ga1-xMnxAstheory vs. experiment
Curie temperature in p-Ga1-xMnxAstheory vs. experiment
• Anomalous Hall effect p uncertain
• Omiya et al.: 27 T, 50 mK
• Theory: TC > 300 K for x > 0.1 and large p
0 1 2 3 4 50
50
100
150
200
THEORY, x = 0.05
Oiwa et al.Van Esch et al.Matsukura et al.Shimizu et al.
Omiya et al.
Ga1-x
MnxAs
CU
RIE
TE
MP
ER
AT
UR
E [
K]
HOLE CONCENTRATION [1020 cm-3]
T.D. et al., PRB’01
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Tuning of magnetic ordering by electrostatic gates (ferro-FET)
Tuning of magnetic ordering by electrostatic gates (ferro-FET)
H. Ohno, .., T.D., ...Nature ‘00
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Ferromagnetic temperature in 2D p-Cd1-xMnxTe QW and 3D Zn1-xMnxTe:N
Ferromagnetic temperature in 2D p-Cd1-xMnxTe QW and 3D Zn1-xMnxTe:N
(k)
(k)
(k)
k
k
k
3D
2D
1D
H. Boukari, ..., T.D., PRL’02 D. Ferrand, ... T.D., ... PRB’01
1020 cm-31018 1019
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1700 1710
1.49 K
1.65
1.87
2.05
2.19
2.80
3.03
4.2 K
0V
PL In
tens
ity (a
.u.)
Energy (meV)
a
1700 1710
1.49 K1.65
1.88
2.05
2.19
2.82
2.97
b4.2 K
-1V
V
QW
barriers
p doped
n doped
undoped
Control byelectrostatic gatein a pin diode –
ferro-LED
Control byelectrostatic gatein a pin diode –
ferro-LED
Hole liquidDepleted
Ev
Ec
EF
V
PRL’02
Photoluminescence
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1700 1710
1.49 K
1.65
1.87
2.05
2.19
2.80
3.03
4.2 K
0V
PL In
tens
ity (a
.u.)
Energy (meV)
a
1700 1710
1.49 K1.65
1.88
2.05
2.19
2.82
2.97
b4.2 K
-1V
Combined: electrostatic gate + illumination
in pin diode (ferro-LED)
Combined: electrostatic gate + illumination
in pin diode (ferro-LED)
Hole liquid Depleted
V
QW
1700 1710
0 V1.5 K
Ev
Ec
EF
Vi ll
um
ina
tio
n
Ferro- diode: electric field and light tuned ferromagnetism
PRL ‘02
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Optical tuning of magnetization - pip diodeOptical tuning of magnetization - pip diode
1680 1690 1700 1710
Tp=161010 cm-2
(a)
4.2 K
2.7 K
2.4 K
2.1 K
1.8 K
1.2 K
Energy [ meV ]
1680 1690 1700 1710
(b)
p
1010
cm-2
2.7
5.2
7.1
10
12
16
T = 1.34 K
Energy [ meV ]
ferromagnetic
paramagnetic
Tem
pera
ture
Hol
e co
ncen
trat
ion
p = const T = const
Illu
min
atio
n
CdMnTe QW 8 nm 0 to 4% Mn
EF
Ev
Ec
PRL’02pip diode: light destroys ferromagnetism
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Zinc-blende ferromagnetic semiconductors- highlights
Zinc-blende ferromagnetic semiconductors- highlights
• Spin injection - (Ga, Mn)As/(Ga,In)As (St. Barbara, Sendai)
• Dimensional effects (Cd,Mn)Te, (Zn,Mn)Te (Grenoble, Warsaw)
• Isothermal transition para <--> ferro - light (In,Mn)As (Tokyo); (Cd,Mn)Te (Grenoble, Warsaw)
- electric field (In,Mn)As (Sendai); (Cd,Mn)Te (Grenoble, Warsaw)
• GMR (Ga, Mn)As/(Al,Ga)As/ (Ga, Mn)As (Sendai)
• TMR (Ga, Mn)As/AlAs/ (Ga, Mn)As (Sendai, Tokyo)
• MCD (Ga, Mn)As (Warsaw, Tsukuba, St. Barbara)
• Strain engineering (Ga, Mn)As (Sedai, Tokyo, Warsaw)
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Chemical trends – hole driven ferromagnetism xMn = 0.05, p = 3.5x1020 cm-3
Chemical trends – hole driven ferromagnetism xMn = 0.05, p = 3.5x1020 cm-3
Materials of light elements:
• large p-d hybridization
• small spin-orbit interaction
T.D. et al., Science ‘00
10 100 1000
C
ZnO
ZnTeZnSe
InAsInP
GaSb
GaPGaAs
GaNAlAs
AlPGe
Si
Curie temperature (K)
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Quantum information hardwareQuantum information hardware
A model of quantum computer, 28Si:31P
Kane, Nature’98cf. Loss, DiVincenzo PRA’98
• qubit: nuclear spin I = ½ of Phosphorous donor impurity
• single qubit operations: A gates affect hyperfine interaction
• two qubit operations: J gates affect e-e exchange interaction
• silicon: 28Si – no nuclear moments, weak spin-orbit interaction
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Towards quantum gates of quantum dotsTowards quantum gates of quantum dots
expl. Delft, Munich, Ottawa, Rehovot, Tokyo, Warsaw, Wuerzburg, ….theory: Basel, Modena, Ottawa, Paris, Sapporo, Wroclaw, …
Spin molecules: cf. B. Barbara talkQuantum optics: cf. A. Zeilinger talk
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Summary: trends in semiconductor spintronics
Summary: trends in semiconductor spintronics
• Physics of spin currents -- injection, transport, coherence, new devices • Spin manipulation -- isothermal and fast magnetization reversal -- single spin manipulation, magnetometry, entanglement • Search for high temperature ferromagnetic
semiconductors -- carrier-controlled ferromagnetism -- intrinsic ferromagnetism warning: precipitates and inclusions often present
Thanks to colleagues in Warsaw and to:I. Solomon, Y. Merle d’Aubigne, H. Ohno, A.H. MacDonald, …