WHAT IS SPINTRONICS? - Delaware Physics › ~bnikolic › teaching › ss_spintronics... ·...
Transcript of WHAT IS SPINTRONICS? - Delaware Physics › ~bnikolic › teaching › ss_spintronics... ·...
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WHAT IS SPINTRONICS?
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What is spintronics?electronics with a spin
GMR (giant magnetoresistance) effect
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GMR hard disk read heads
From: IBM web site
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GOAL
• spin control of electrical properties(I-V characteristics)
• electrical control of spin(magnetization)
Applications:•magnetic read heads•nonvolatile RAM•quantum computing (?)
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New directionssemiconductor spintronics
• spin field-effect devices• magnetic semiconductor tunnel junction devices• magnetic bipolar junction devices• spin optoelectronics• spin galvanics• mesoscopic spintronics• spin-polarized semiconductor lasers• spin torque• spin quantum computing• ...
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Datta-Das Spin FETS. Datta and B. Das, Appl. Phys. Lett. 56, 665 (1990)
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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SPINTRONICS’ 3 REQUIREMENTS
• EFFICIENT SPIN INJECTION
• SLOW SPIN RELAXATION
• RELIABLE SPIN DETECTION
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MRFM single spin detection(magnetic resonance force microscopy)
IBM web site D. Rugar et al., Nature 430, 329 (2004)
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OPTICAL SPIN ORIENTATION
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Zincblende band structureoptical orientation transitions
σ+σ+
mj
Eg
∆
CB
SO
E
LH
HH
0 k
(a)
3/2P
1/2P
1/2S (b)
HH,LH
σ− −σ
1/2−1/2
−1/2 1/2
−3/2 3/2
−1/2 1/2
SO
CB
3 1 1 3
22Γ7
Γ8
6Γ
so
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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Zincblende k=0 Bloch statessymmetries
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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Dresselhaus (BIA) and Bychkov-Rashba field patterns
SIA
[111]BIA
[001]BIA
BIA [110]
110110
001
100010
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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SPIN RELAXATION and SPIN DYNAMICS
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Spin relaxation in metals:Elliott-Yafet theory
R. J. Elliott, Phys. Rev. B 96, 266 (1954)Y. Yafet, in Solid State Physics, Vol. 14, p.2 (1963)
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=
__
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Phonon-induced spin relaxation in aluminum
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Spin relaxation in bulk n-GaAs
τττττ
τ
relaxationtim
e(ns)
R. I. Dzhioev et al., Phys. Rev. B 66, 245204 (2002)
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Spin relaxation in GaAs/AlGaAs QWvs confinement energy (DP--quadratic)
E1e (m eV)0 20 40 60 80 100 120 140
SpinRelaxationRate(ps-1)
0.00
0.02
0.04
0.06
0.08
0.10
A. R. Malinowski et al. Phys. Rev. B 62, 13034 (2000).
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SPIN INJECTION
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F/N spin injection
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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spin injection into semiconductors• Theoretically predicted by
A. G. Aronov and G. E. Pikus, Fiz. Tekh. Poluprovodn. 10, 1177 (1976) [Sov. Phys. Semicond. 10, 698-700 (1976)]
• Experimentally first realized byM. Johnson and R. H. Silsbee, Phys. Rev. Lett. 55, 1790 (1985)
• Experimental realization in semiconductors:
Fiederling et al. Nature 402, 787 (1999).Ohno et al. Nature 402, 790 (1999).
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Electroluminescence in a ZnMnSeLED
0
20
40
60
80
100
0 1 2 3 4 5 6 7 8
EL
Po
lariza
tio
n(%
)
Magnetic Field (T)
T = 4.5 K
1.52 1.53 1.54 1.55 1.56 1.57
EL
Inte
nsity
(arb
.u
nits)
Photon Energy (eV)
0
0.5
2
4 T
T = 4.5 K�+
�-
(a) (b)
B. T. Jonker et al., App. Phys. Lett. 79, 3089 (2001)
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F/I/F tunnel junction
F2F1 F2F1
(a)
E E
I I
(b)
E E
N (E) N (E) N (E) N (E) N (E) N (E) N (E) N (E)
∆ex
subbandminority−spin majority−spin
subband
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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SPINTRONIC DEVICES
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Datta-Das Spin FETS. Datta and B. Das, Appl. Phys. Lett. 56, 665 (1990)
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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Magnetic tunnel transistor
M
Fermi level
CoFeGaAs
IC
VBCVEB
eVEB IECoFe
Emitter
Base
Collector
Fermi level
Al O2 3
�
M1
2 34
A
S. Van Dijken, PRL 90, 197203 (2003)
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Loss-DiVincenzospin quantum computer
D. Loss and D. P. DiVincenzo, PRA 57, 120 (1998).
From: I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004)
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magnetic bipolar diode
Make use of the existing device structures
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CONVENTIONAL DIODE 101
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p-n junction formation
before:
during:
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p-n junction diode
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p-n junction diodeequilibrium
p region: holes n region: electrons
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equilibrium currents
thermal generationthermal activation
in equilibrium Jf=Jr=Jg
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p-n junction diodenonequilibrium
p region n region
Forward bias: J=Jg exp(V/kBT) Reverse bias: J=Jg
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Magnetic bipolar diode(giant) magnetoresistance
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Magnetic Bipolar Diode spin in equilibrium:
no spin-charge coupling
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Spin-charge coupling:large current
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Spin-charge coupling:small current
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GMR in MBT numericallyspin-voltaic effect
V=0.8 VGaAs
I. Zutic, J. Fabian, and S. Das Sarma, Phys. Rev. Lett. 88, 066603 (2002).
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spin injection?
ONLY AT LARGE BIASES!
I. Zutic, J. Fabian,S. Das Sarma, Phys. Rev. B. 64, 121201 (2001).
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spin-polarized bipolar transport
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Bipolar spin-polarized transportnumerical modeling
• electron and hole drift in external + intrinsic E-field• electron and hole diffusion• magnetic drift (Stern-Gerlach-like)• spin diffusion• electron-hole recombination• spin relaxation• Poisson’s equation (selfconsistency)
+ boundary conditions (ohmic contacts, spin injection)
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magnetic bipolar transistor
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CONVENTIONAL TRANSISTOR 101
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Magnetic Bipolar Transistor
J. Fabian, I. Zutic and S. Das Sarma, Appl. Phys. Lett. 84, 85 (2004);J. Fabian and I. Zutic, Phys. Rev. B 69, 115314 (2004).
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MBTintrinsic spin extraction/injection
efficiency exp(qVbe/kBT)
104
106
108
1010
1012
1014
1016
1018
n, s
(cm
-3)
electron density nspin density s
0 1 2 3 4 5x (µ)
00.20.40.60.8
α
0 1 2-10
-3
0
magnetic baseP0=0.67Vbe=0.5 VVbc=0 V
J. Fabian and I. Zutic, Phys. Rev. B 69, 115314 (2004)
![Page 58: WHAT IS SPINTRONICS? - Delaware Physics › ~bnikolic › teaching › ss_spintronics... · 2004-08-08 · What is spintronics? electronics with a spin GMR (giant magnetoresistance)](https://reader034.fdocuments.net/reader034/viewer/2022042400/5f0eef417e708231d441a948/html5/thumbnails/58.jpg)
GIANT MAGNETOAMPLIFICATION EFFECT
J. Fabian and I. Zutic, Phys. Rev. B 69, 115314 (2004)