Hitachi Cambridge Laboratory, UK

1
Spin Hall effect
J. Wunderlich(1), B. Kaestner(1,2), J. Sinova
(3), T. Jungwirth (4,5)

• Hitachi Cambridge Laboratory, UK
• National Physical Laboratory, UK
• Texas AM University, USA
• Institute of Physics ASCR, Czech Republic
• University of Nottingham, UK

Collaborators Allan MacDonald, Dimitri Culcer,
Ewelina Hankeiwc, Qian Niu, Kentaro Nomura,
Nikolai Sinitsyn, Laurens Molenkamp, Winfried
Teizer
2
OUTLINE - Theory remarks - Comments on
experiments
Kerr microscope
Co-planar spin LED
SHE in a bulk semiconductor
SHE in a 2D hole gas
Kato et. al., Science 306, 1910
Wunderlich et. al., Phys. Rev. Lett. 94, 047204
3
SHE - Theory (http//unix12.fzu.cz/msnew)
Schmeltzer2005_a D. Schmeltzer, "The
Non-Dissipative Spin-Hall Conductivity and the
Identification of the Conserved Current", (2005),
preprint cond-mat/0504035 on-line Wu2005_a M.
W. Wu and J. Zhou, "Spin-Hall effect in
two-dimensional mesoscopic hole systems", (2005),
preprint cond-mat/0503616 on-line Erlingsson2005
_a Sigurdur I. Erlingsson and Daniel Loss,
"Determining the spin Hall conductance via charge
transport", (2005), preprint cond-mat/0503605
on-line Zhang2005_b Ping Zhang and Junren Shi
and Di Xiao and Qian Niu, "Conserved Effective
Spin Current in Spin-Orbit Coupled Systems",
(2005), preprint cond-mat/0503505
on-line Sugimoto2005_a Naoyuki Sugimoto,
Shigeki Onoda, Shuichi Murakami, Naoto Nagaosa,
"Intrinsic vs. extrinsic spin Hall effect in the
disordered Rashba Mode", (2005), preprint
cond-mat/0503475 on-line Bleibaum2005_a O.
Bleibaum, "Spin-Hall effect in a dirty Rashba
semiconductor", (2005), preprint
cond-mat/0503471 on-line Nikolic2005_a
Branislav K. Nikolic, Liviu P. Zarbo, and Sven
Welack, "Where is transverse "force" in the
intrinsic spin Hall effect?", (2005), preprint
cond-mat/0503415 on-line Liu2005_b S. Y. Liu
and X. L. Lei, "Disorder effects on
dissipationless spin-Hall current in a diffusive
Rashba two-dimensional heavy-hole system",
(2005), preprint cond-mat/0503352
on-line Hu2005_b Jiangping H, "Topological
orbital angular momentum Hall current", (2005),
preprint cond-mat/0503149 on-line Chen2005_a
W.Q. Chen, Z.Y. Weng, and D.N. Sheng, "Numerical
Study of the Spin Hall Conductance in the
Luttinger Model", (2005), preprint
cond-mat/0502570 on-line Entin-Wohlman2005_a
O. Entin-Wohlman, A. Aharony, Y. M. Galperin, V.
I. Kozub, and V. Vinokur, "Orbital ac spin-Hall
effect in the hopping regime", (2005), preprint
cond-mat/0502478 on-line Liu2005_a S. Y. Liu
and X. L. Lei, "Vanishing of the Dissipationless
Spin Hall Effect in a Diffusive Two-Dimensional
Electron Gas with Spin-Orbit Coupling", (2005),
preprint cond-mat/0502392 on-line Yao2005_a Y.
Yao, and Z. Fang, "Intrinsic Spin Hall Effect in
Semiconductors and Simple Metals
First-Principles Calculations", (2005), preprint
cond-mat/0502351 on-line Bernevig2005_a B.
Andrei Bernevig, Taylor L. Hughes, Shou-Cheng
Zhang, "Orbitronics the Intrinsic Orbital Hall
Effect in p-Doped Silicon", (2005), preprint
cond-mat/0502345 on-line Li2005_a Jian Li,
Liangbin Hu, and Shun-Qing Shen, "Spin resolved
Hall effect driven by spin-orbit couplin",
(2005), preprint cond-mat/0502102
on-line Hu2005_a Jiangping Hu, "Spin
Polarization and Dichroism Effects by Electric
Field", (2005), preprint cond-mat/0502005
on-line Lou2005_a Ping Lou and Tao Xiang, "Spin
Hall current and two-dimensional magnetic
monopole in a Corbino disk", (2005), preprint
cond-mat/0501307 on-line Nikolic2004_b Nikolic
et al., "Non-Equilibrium Spin Accumulation due to
the Spin Hall Effect in Mesoscopic Two-Probe
Ballistic Spin-Orbit ", (2004), preprint
cond-mat/0412595 on-line Bernevig2004_e B.
Andrei Bernevig and Shou-Cheng Zhang, "Intrinsic
Spin-Hall Effect in n-Doped Bulk GaAs", (2004),
preprint cond-mat/0412550 on-line Kou2004_a
Su-Peng Kou, Xiao-Liang Qi, and Zheng-Yu Weng,
"Conserved Dissipationless Spin Currents in a
Doped Mott Insulator", (2004), preprint
cond-mat/0412146 on-line Mele2004_a C.L. Kane
and E.J. Mele, "Quantum Spin Hall Effect in
Graphene", (2004), preprint cond-mat/0411737
on-line Bernevig2004_d B. Andrei Bernevig,
Xiaowei Yu, Shou-Cheng Zhang, "Maxwell Equation
for the Coupled Spin-Charge Wave Propagation",
(2004), preprint cond-mat/0411276 on-line
4
Sun2004_a Qing-feng Sun, Jian Wang, Hong Guo,
"Quantum transport theory for nanostructures with
Rashba spin-orbital interaction", (2004),
preprint cond-mat/0411469 on-line Shekhter2004_a
A. Shekhter, et al., "Chiral spin resonance and
spin-Hall conductivity in the presence of the
electron-electron interactions", (2004), preprint
cond-mat/0411239 on-line Serebrennikov2004_a
Yuri A. Serebrennikov, "Gometric spin dephasing
of carriers with strong spin-orbit coupling",
(2004), preprint cond-mat/0411683
on-line Chang2004_a Ming-Che Chang, "The effect
of in-plane magnetic field on the spin Hall
effect in Rashba-Dresselhaus system", (2004),
preprint cond-mat/cond-mat/0411697
on-line Liu2004_d S. Y. Liu, X. L. Lei, "Spin
Hall Effect in a Diffusive Rashba Two-dimensional
Electron Gas", (2004), preprint cond-mat/0411629
on-line Bernevig2004_c B. Andrei Bernevig and
Shou-Cheng Zhang, "Intrinsic Spin Hall Effect in
the Two Dimensional Hole Gas", (2004), preprint
cond-mat/0411457 on-line Mal'shukov2004_a A.G.
Mal'shukov and K.A. Chao, "Spin-Hall conductivity
of a disordered 2D electron gas with Dresselhaus
spin-orbit interaction", (2004), preprint
cond-mat/0410607 on-line Souma2004_a Satofumi
Souma and Branislav K. Nikolic, "Spin Hall
Current Driven by Quantum Interferences in
Mesoscopic Rashba Rings", (2004), preprint
cond-mat/0410716 on-line Shen2004_b Shun-Qing
Shen, et al., "Resonant spin Hall conductance in
quantum Hall systems lacking bulk and structural
inversion symmetry", (2004), preprint
cond-mat/0410169 on-line Sheng2004_a L. Sheng,
D. N. Sheng, and C. S. Ting, "Spin-Hall Effect in
Two-Dimensional Electron Systems with Rashba
Spin-Orbit Coupling and Disorder", (2004),
preprint cond-mat/0409038 on-line Nikolic2004_a
Branislav K. Nikolic, Liviu P. Zarbo, and
Satofumi Souma, "Mesoscopic Spin Hall Effect in
Multiprobe Semiconductor Bridges", (2004),
preprint cond-mat/0408693 on-line Bernevig2004_b
B. Andrei Bernevig and Shou-Cheng Zhang, "Spin
Splitting and Spin Current in Strained Bulk
Semiconductors", (2004), preprint
cond-mat/0408442 on-line Khaetskii2004_a
Alexander Khaetskii, "Nonexistence of intrinsic
spin currents", (2004), preprint
cond-mat/0408136 on-line Rashba2004_c Emmanuel
I. Rashba, "Spin Dynamics and Spin Transport",
(2004), preprint cond-mat/0408119
on-line Wang2004_b Xindong Wang and X.-G.
Zhang, "Spin symmetry and spin current of
helicity eigenstates of the Luttinger
Hamiltonian", (2004), preprint cond-mat/0407699
on-line Dimitrova2004_b Ol'ga V. Dimitrova,
"Spin-Hall Conductivity and Pauli Susceptibility
in the Presence of Electron-Electron
Interactions", (2004), preprint cond-mat/0407612
on-line Chalaev2004_a Oleg Chalaev, Daniel
Loss, "Spin-Hall conductivity due to Rashba
spin-orbit interaction in disordered systems",
(2004), preprint cond-mat/0407342
on-line Schmeltzer2004_a D. Schmeltzer,
"Topological spin current", (2004), preprint
cond-mat/0406565 on-line Zhang2004_a Ping
Zhang and Qian Niu, "Charge-Hall effect driven by
spin force reciprocal of the spin-Hall effect",
(2004), preprint cond-mat/0406436
on-line Dimitrova2004_a Ol'ga V. Dimitrova,
"Universal value of Spin-Hall Conductivity of 2D
Rashba metal with impurities", (2004), preprint
cond-mat/0405339 on-line Murakami2004_a
Shuichi Murakami, "Spin Hall Effect in p-type
Semiconductors", (2004), preprint
cond-mat/0405003 on-line Xiong2004_a Ye Xiong
and X.C. Xie, "Spin Hall Conductance in
Disordered Two-Dimensional Electron Systems",
(2004), preprint cond-mat/0403083
on-line Dyakonov2004_a M. I. Dyakonov,
"Spintronics?", (2004), preprint
cond-mat/0401369 on-line -------- 2005 -------- R
aimondi2004_a Roberto Raimondi and Peter
Schwab, "Spin-Hall effect in a disordered 2D
electron-system", Phys. Rev. B 71, 033311 (2005)
on-line, preprint cond-mat/0408233
on-line Zhang2004_b S. Zhang and Z. Yang,
"Intrinsic Spin and Orbital-Angular-Momentum Hall
Effect", Phys. Rev. Lett. 94, 066602 (2005)
on-line, preprint cond-mat/0407704 on-line
5
Nomura2004_a K. Nomura, et al., "Non-vanishing
spin Hall currents in disordered spin-orbit
coupling systems", Phys. Rev. B 71, 041304
(2005) on-line, preprint cond-mat/0407279
on-line Schliemann2004_a John Schliemann,
Daniel Loss, "Spin-Hall transport of heavy holes
in III-V semiconductor quantum wells", Phys. Rev.
B 71, 085308 (2005) on-line, preprint
cond-mat/0405436 on-line -------- 2004 -------- R
ashba2004_d Emmanuel I. Rashba, "Sum rules for
spin-Hall conductivity cancelation", Physica B
70, 201309(R) (2004) on-line, preprint
cond-mat/0409476 on-line Hankiewicz2004_b E.
M. Hankiewicz, et al., "Manifestation of the
spin-Hall effect through transport measurements
in the mesoscopic regime", Phys. Rev. B 70,
241301(R) (2004) on-line, Ma2004_a Xiaohua
Ma, et al., "Influences of spin accumulation on
the intrinsic spin Hall effect in two dimensional
electron gases with Rashba spin-orbit coupling",
Phys. Rev. B 70, 195343 (2004) on-line,
Mishchenko2004_a E.G. Mishchenko, et al.,
"Spin current and polarization in impure 2D
electron systems with spin-orbit coupling", Phys.
Rev. Lett. 93, 226602 (2004) on-line, preprint
cond-mat/0406730 on-line Bernevig2004_a B. A.
Bernevig, "On the nature of spin currents", Phys.
Rev. B 71, 073201 (2004) on-line, preprint
cond-mat/0406153 on-line Murakami2004_b
Shuichi Murakami, Naoto Nagaosa, Shou-Cheng
Zhang, "Spin Hall Insulator", Phys. Rev. Lett.
93, 156804 (2004) on-line, preprint
cond-mat/0406001 on-line Lee2004_a Wei-Li Lee,
et al., "Dissipationless Anomalous Hall Current
in the Ferromagnetic Spinel CuCr2Se4-xBrx",
Science 303, 1647 (2004) on-line, preprint
cond-mat/0405584 on-line Zutic2004_a Igor
Zutic, Jaroslav Fabian and S. Das Sarma,
"Spintronics Fundamentals and applications",
Rev. Mod. Phys. 76, 323 (2004) on-line, preprint
cond-mat/0405528 on-line Murakam2004_a Shuichi
Murakami, "Absence of vertex correction for the
spin Hall effect in p-type semiconductors", Phys.
Rev. B 69, 241202 (2004) on-line, preprint
cond-mat/0405001 on-line Rashba2004_b Emmanuel
I. Rashba, "Spin currents, spin populations, and
dielectric function", Phys. Rev. B 70, 161201
(2004) on-line, preprint cond-mat/0404723
on-line Shen2004_a Shun-Qing Shen, et al.,
"Resonant Spin Hall Conductance in
Two-Dimensional Electron Systems with Rashba
Interaction in a Magnetic Field", Phys. Rev. Lett
92, 256603 (2004) on-line, Inoue2004_a
Jun-ichiro Inoue, et al., "Suppression of the
Persistent Spin Hall Current by Defect
Scattering", Phys. Rev. B 70, 041303 (2004)
on-line, preprint cond-mat/0402442
on-line Hu2004_a Liangbin Hu, et al., "Effects
of spin imbalance on the electric-field-driven
quantum dissipationless spin current in p-doped
semiconductors", Phys. Rev. B 70, 235323 (2004)
on-line, Bernevig2003_a Bogdan et al.,
"Dissipationless spin current in anisotropic
p-doped semiconductors", Phys. Rev. B 70, 113301
(2004) on-line, preprint cond-mat/0311024
on-line Shen2003_a Shun-Qing Shen, "Spin Hall
effect and Berry phase in two dimensional
electron gas", Phys. Rev. B 70, 081311 (2004)
on-line, preprint cond-mat/0310368
on-line Sinitsyn2003_a N. A. Sinitsyn, et al.,
"Spin-Hall and spin-diagonal conductivity in the
presence of Rashba and Dresselhaus spin-orbit
coupling", Phys. Rev. B 70, 081312(R) (2004)
on-line, Schliemann2004_b John Schliemann and
Daniel Loss, "Dissipation effects in spin-Hall
transport of electrons and holes", Phys. Rev. B
69, 165315 (2004) on-line, preprint
cond-mat/0310108 on-line Culcer2004_a Dimitrie
Culcer, et al., "Semiclassical theory of spin
transport in spin-orbit coupled systems", Phys.
Rev. Lett. 93, 046602 (2004) on-line, preprint
cond-mat/0309475 on-line -------- 2003 -------- R
ashba2003_a Emmanuel I. Rashba, "Spin currents
in thermodynamic equilibrium The challenge of
discerning transport currents", Phys. Rev. B 68,
241315 (2003) on-line Culcer2003_a Dimitrie
Culcer, Allan MacDonald, Qian Niu, "Anomalous
Hall effect in paramagnetic two dimensional
systems", Phys. Rev. B 68, 045327 (2003)
on-line, preprint cond-mat/0311147
on-line Hu2003_a Jiangping Hu, Bogdan A.
Bernevig and Congjun Wu, "Spin current in
spin-orbit coupling systems", Int. J. Mod. Phys.
B 17, 5991 (2003), preprint cond-mat/0310093
on-line Murakami2003_b Shuichi Murakami, et
al., "SU(2) Non-Abelian holonomy and
dissipationless spin current in semiconductors",
Phys. Rev. B B 69, 235206 (2003) on-line,
preprint cond-mat/0310005 on-line Sinova2004_a
Jairo Sinova, et al., "Universal Intrinsic
Spin-Hall Effect", Phys. Rev. Lett. 92, 126603
(2004) on-line, preprint cond-mat/0307663
on-line Murakami2003_a Shuichi Murakami, Naoto
Nagaosa, Shou-Cheng Zhang, "Dissipationless
Quantum Spin Current at Room Temperature",
Science 301, 1348 (2003) on-line, preprint
cond-mat/0308167 on-line --------
6
SHE - Experiment (http//unix12.fzu.cz/msnew)
Kato2005_a Y. K. Kato, et al., "Electrical
initialization and manipulation of electron spins
in an L-shaped strained n-InGaAs channel",
(2005), preprint cond-mat/0502627
on-line Wunderlich2004_a  J. Wunderlich, et al.
"Experimental observation of the spin-Hall effect
in a two dimensional spin-orbit coupled
semiconductor system", Phys. Rev. Lett. 94,
047204 (2005) preprint cond-mat/0410295
on-line Kato2004_d  Y. K. Kato, R. C. Myers, A.
C. Gossard, and D. D. Awschalom, "Observation of
the Spin Hall Effect in Semiconductors", Science
306, 1910 (2004) on-line
7
Ordinary and quantum Hall effects
Lorentz force deflect like-charge particles
Quantum Resistance standard fractional-charge
carriers
Ordinary Sign and density of carriers holes
in SC
8
Anomalous Hall effect
Spin-orbit coupling force deflects like-spin
particles
InMnAs
Simple electrical measurement of magnetization
9
Spin Hall effect
Spin-orbit coupling force deflects like-spin
particles
Spin-current generation in non-magnetic systems
without applying external magnetic fields
Spin accumulation without charge
accumulation excludes simple electrical detection
10
Spin-orbit coupling (relativistic effect)
Produces an electric field
Ingredients - potential V(r)
- motion of an electron
E
In the rest frame of an electron the electric
field generates and effective magnetic field
- gives an effective interaction with the
electrons magnetic moment
11
Skew scattering off impurity potential (Extrinsic
SHE/AHE)
If only this SO effect then much too weak to give
a sizable SHE/AHE
12
SO-coupling from host atoms (Intrinsic SHE/AHE)
l0 for electrons ? weak SO l1 for holes ?
strong SO
Enhanced in asymmetric QW
13
Intrinsic AHE approach explains many experiments

• (Ga,Mn)As systems Jungwirth et al. PRL 02, APL
  03
• Fe Yao, Kleinman, Macdonald, Sinova,
• Jungwirth et al PRL 04
• Layered 2D ferromagnets such as SrRuO3 and
  pyrochlore ferromagnets Onoda and Nagaosa, J.
  Phys. Soc. Jap. 01,Taguchi et al., Science 01,
  Fang et al Science 03, Shindou and Nagaosa, PRL
  01
• Manganites, Ye et al. PRL 99
• Ferromagnetic spinel CuCrSeBr Lee et al. Science
  04

Experiment sAH ? 1000 (W cm)-1 Theroy sAH ? 750
(W cm)-1
14
INTRINSIC SPIN-HALL EFFECT Murakami, Nagaosa,
Zhang, Science 2003 (cond-mat/0308167)Sinova,
Culcer, Niu, Sinitsyn, Jungwirth, MacDonald, PRL
2004 (cont-mat/0307663)
Lets start with a simple model Rashba SO
coupling in a 2DEGs
Inversion symmetry ? no R-SO
Broken inversion symmetry ? R-SO
Bychkov and Rashba 84
15
Heuristic argument z-component of spin due to
precession in effective "Zeeman" field
Classical dynamics in k-dependent (Rashba) field
LLG equations for small drift ? adiabatic
solution
?
16
Spin Hall conductivity
17
Classical and Kubo formula give the same
spin-Hall conductivity
Color plot of spin-Hall conductivity yellowe/8p
and red0
18
Disorder effects finite lifetime (Born
approximation) for Rashba 2DEG
? intrinsic SHE
19
Disorder effects beyond the Born approximation
for Rashba 2DEG
Question Are there any other major effects
beyond the finite life time broadening? Can
vertex corrections be ignored?
Mal'shukov et al, PRL 04 Raimondi et al, PRB
04 Khaetskii, cond-mat/0408136 Loss et al,
cond-mat/0407342 v2
Inoue, Bauer, Molenkamp PRB 04
Ladder sum vertex correction
20
Spin Hall effect ?
Intrinsic ? cancelled by vertex corrections for
infinitely weak disorder
Extrinsic ? too weak to give
any sizable effect
21
Ways to solve (go around) the controversy
- Skew scattering in SO-coupled bands in the
spirit of Dyakonov and Perel PLA '71 and
Hirsch PRL '99 ? no detailed theory done yet
- Intrinsic SHE in Rashba-SO systems beyond
perturbation theory by solving Kubo formula
exactly ? inconclusive (finite-size
effects) Nomura et al. PRB '05 -
Other than Rashba-SO systems (intrinsic AHE
explains experiments here)
Bernevig, Zhang, cond-mat/0411457, cond-mat/04125
50
? vertex corrections vanish in all other
studied SO-systems (bulk, 2DHG,..)
22
- Look at transport in mesoscopic systems instead
of conductivity in the thermodynamic limit

Nikolic et al., cond-mat/0412595
Hankiewicz et al., PRB 04
SHE in 2DHG more robust than in Rashba 2DEG
23
- Measure the effect
Kato, Myars, Gossard, Awschalom, Science 306,
1910 "Observation of the spin Hall effect
in semiconductors" Local Kerr effect in
n-type GaAs and InGaAs 0.03 polarization
Bulk semiconductor ? stronger disorder n-type
material ? weaker SO-coupling
Not in the intrinsic SHE regime
24
Wunderlich, Kästner, Sinova, Jungwirth, Phys.
Rev. Lett. 94, 047204 Experimental observation
of the spin-Hall effect in a two dimensional
spin-orbit coupled semiconductor system
Co-planar spin LED in GaAs 2D hole gas 1
polarization
25
Self-consistent LDA 6-band calculations for
the 001 QW
Modulation doping ? weak disorder p-type
asymmetric QW ? strong SO
Close to the intrinsic SHE regime
26
A dissipationless remark ...
27
Dissipative spin-polarized currents in
non-magnetic systems at B0
Spin-current is along the applied electric field
? proportional to non-equilibrium distribution
function
asymmetric scattering involving spin-flip
Ganichev et al., cond-mat/0403641, Silov et al.
APL 04
28
Dissipationless intrinsic spin Hall effect
? Heuristic argument transverse spin current
generated between scattering events
Sinova, Culcer, Niu, Sinitsyn, Jungwirth, MacDonal
d, PRL 92, 126603 (2004)
? Boltzman equation for current transverse
anomalous velocity in the equilibrium band
structure due to combined E and SO effects
Jungwirth, Niu, MacDonald, Phys. Rev. Lett.
(2002) Murakami, Nagaosa, Zhang, Science 301,
1348-1351 (2003).
normal group velocity
anomalous velocity
Berry curvature M.V. Berry, Proc. Royal Soc.
London (1984)
29
Caution the dissipationless transverse intrinsic
SHE is accompanied by a
dissipative longitudinal response to the electric
field
30
Conventional vertical spin-LED
Novel co-planar spin-LED
Y. Ohno et al. Nature 402, 790 (1999) R.
Fiederling et al. Nature 402, 787 (1999) B. T.
Jonker et al. PRB 62, 8180 (2000) X. Jiang et
al. PRL 90, 256603 (2003) R. Wang et al. APL
86, 052901 (2005)
? Light emission near edge of the 2DHG ? 2DHG
with strong and tunable SO ? Spin detection
directly in the 2DHG ? No hetero-interface
along the LED current
2DHG
2DEG
Spin polarization detected through circular
polarization of emitted light
31
Conventional vertical spin-LED
Novel co-planar spin-LED
Y. Ohno et al. Nature 402, 790 (1999) R.
Fiederling et al. Nature 402, 787 (1999) B. T.
Jonker et al. PRB 62, 8180 (2000) X. Jiang et
al. PRL 90, 256603 (2003) R. Wang et al. APL
86, 052901 (2005)
? No hetero-interface along the LED current ?
Spin detection directly in the 2DHG ? Light
emission near edge of the 2DHG ? 2DHG with
strong and tunable SO
2DHG
2DEG
Spin polarization detected through circular
polarization of emitted light
32
CO-PLANAR pn - JUNCTION
Wafer design based on Schrödinger-Poisson
simulations
33
n - region
p - region
? 2D transport characteristics
Carrier density n 0.8 ? 1012 cm-2
p 2.0 ? 1012 cm-2
Mobility µHn ? 2900 cm2/Vs
µHp ? 3400 cm2/Vs
pn - junction
? Light emission near junction in p-region
? Light emission for e VBias ? EG
? Rectifying
Reverse breakdown VR -11.5V (T 4.2K)
34
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35
Sub GaAs gap spectra analysis PL vs EL

X bulk GaAs excitons I recombination with
impurity states
36
Sub GaAs gap spectra analysis PL vs EL


-
X bulk GaAs excitons I recombination with
impurity states B (A,C) 3D electron 2D
hole recombination
37
Sub GaAs gap spectra analysis PL vs EL


--
X bulk GaAs excitons I recombination with
impurity states B (A,C) 3D electron 2D
hole recombination
Bias dependent emission wavelength for 3D
electron 2D hole recombination A. Y. Silov et
al., APL 85, 5929 (2004)
38
CONTROL EXPERIMENT
p-n junction current only (no SHE driving
current)
39
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40
Circular Polarization of EL detected at
perpendicular to 2DHG plane
41
Inplane Circular Polarization (? 85º) detected
at B 3T.
42
Inplane Circular Polarization (? 85º) detected
at B ? 3T.
43
Circular Polarization
In-plane detection angle
44
Circular Polarization
In-plane detection angle
Perp.-to plane detection angle
? NO perp.-to-plane component of polarization at
B0 ? B?0 behavior consistent with SO-split HH
subband
45
Spin Hall Effect

• Perpendicular-to-plane spin-polarization

46
EXPERIMENT Spin Hall Effect
47
Spin Hall Effect Device
48
Experiment A
Experiment B
Opposite perpendicular polarization for opposite
Ip currents or opposite edges ? SPIN HALL
EFFECT