Spin Valves - phy.pku.edu.cn

© 2014 ICQM

Chapter 4

Spin Valves

韩伟

量子材料科学中心

2021年05月07日

2

1. Metal Spin Valves

Local and Nonlocal spin valves

Hanle spin precession

Nano devices (Thanks to cleanroom)

Spin injection efficiency

Spin relaxation in Metals: EY mechanism

Review of this class

3

Review of last class

4


Spin Injection efficiency

5

Jedema, et al, PRB 67, 085319 (2003) Fabian & Das Sarma, PRL 81, 5624 (1998)


6

Summary

1. Semiconductor Spin Valves

When spintronics meets semiconductor

GaAs

Silicon and Germanium

Spin FET

Dynamic spin injection

7

This Class

3. Spin valves based on Superconductors and Quantum materials

8

Outline

1. Superconductor Spin Valves

Large MR

Spin injection, Long spin lifetime

Large spin Hall effect

Spin-Triplet

9

Superconductor

Onnes, Commun. Phys. Lab. (1911)

10

"Door meten tot weten" (Knowledge through measurement)

Superconductor

11

Superconductor

12

Ferromagnetism vs.Superconductor

13

Ferromagnetism vs.Superconductor

14

本课程共九章

一、自旋电子学简介

二、磁性和磁性材料

三、磁阻效应

四、自旋阀

五、自旋转移力矩

六、热自旋电子学

七、拓扑自旋流

八、反铁磁自旋电子学

九、超导自旋电子学

学习了解一些自旋电子学研究进展

15

Superconductor

Pena, et al, PRL 94, 057002 (2005)

LaCaMnO—YBaCuO—LaCaMnO multilayers

16

Superconductor

Miao, et al, PRL 101, 137001 (2008)

17

Superconductor

18

Superconductor

19

Superconductor

20

Superconductor

Nb (S)—BaFe12O19 (FM) Domain wall superconductivity

Yang, et al, Nature Materials, 3 , 793–798 (2004)

21

Spin injection into Superconductor

22


Yang, et al, Nature Materials, 9 , 586–593 (2010)

23


24


Long spin lifetime

25


Al

Quay, et al, Nature Physics, 9 , 84–88 (2013)

26


Transition from N S

27


Transition from N S

28


Transition from N S

29


Spin absorption by Nb

Wakamura, et al, PRL, 112, 036602 (2014)

30


31

Spin Hall in Superconductor

Wakamura, et al, Nature Materials, 14 , 675–678 (2015)

32


Wakamura, et al, Nature Materials, 14 , 675–678 (2015)

33


34

Spin pumping into Superconductor

Yao, et al, PRB, 97, 224414 (2018)

35

Josephson junction

Single electron tunneling? Tunneling as a pair?

VS

36

Spin Triplet

Keizer, et al, Nature, 439 , 825–827 (2006)

37

Spin Triplet

Robinson, et al, Science, 329, 59-61 (2010)

38

FM SC SS

H

M

Spin triplet

Jeon, et al, Nature Materials, 17 , 499–503 (2018)

39

本课程共九章

一、自旋电子学简介

二、磁性和磁性材料

三、磁阻效应

四、自旋阀

五、自旋转移力矩

六、热自旋电子学

七、拓扑自旋流

八、反铁磁自旋电子学

九、超导自旋电子学

学习了解一些自旋电子学研究进展

© 2014 ICQM

休息10分钟

41

42

Outline

2. Spin valves based on Quantum materials

石墨烯弱自旋-轨道耦合长自旋寿命

二硫化钼等自旋-谷

拓扑绝缘体自旋流的拓扑保护

4343

conductivity mismatch

Small spin signal (mainly work at low temperatures)

Short spin lifetimesLarge velocity of electrons

Conductivity similar to FM

RT operation

Disadvantages Advantages

Metals Semiconductors

Advantages Disadvantages

Long spin lifetimes

Tunable carrier density

Graphene

4444

conductivity mismatch

Small spin signal (mainly work at low temperatures)

Short spin lifetimes

Disadvantages

Metals Semiconductors

Disadvantages

Graphene combines the advantages of both metals and semiconductors

Graphene

Large velocity of electrons

Conductivity similar to FM

RT operation

AdvantagesAdvantages

Long spin lifetimes

Tunable carrier density

Graphene

4545

Graphite Graphene

Massless Dirac FermionsSemimetal

k

E

EF

k

E

EF

Spin-dependent properties

Long spin lifetime(~ µs)

Low intrinsic spin-orbit coupling

High mobility

Long spin transport length

Gmitra, et al, Phys. Rev. B, 79, 012403 (2009)Abdelouahed, et al, Phys. Rev. B, 82, 125424 (2010)

D

Graphene

4646

Graphene spin devicesE3 E4E2E1

Si

SiO2

Electrostatic gate

Vgate

Graphene

MgOCo Ti

Samples

10 µm

Graphene spin valves

47

)exp()(

,0,0

0

xx

tB

Diffuse without precession


48

Transparent contact Pinhole contact Tunneling contact

Co

graphene

MgOCo

graphene

MgOCo

graphene

Co

graphene

Co

graphene

MgO

E.I. Rashba, Phys. Rev. B 62, 16267(R) (2000) A. Fert, H. Jaffres, Phys. Rev. B 64, 184420 (2001).


49

Transparent contact

Co

graphene

ΔRNL

T = 300 K

-40 -20 0 20 40

-100

-50

0

50

100

H (mT)

RN

L(m

Ω)

Nonlocal MR: ~ 0.1 ohmsSpin injection efficiency: ~ 1 %


50

Pinhole contact

MgOCo

graphene

-6 0 -4 0 -2 0 0 2 0 4 0 6 0

-2

0

2

4L = 2 m

R(

)

H (m T )

T = 3 0 0 K

Nonlocal MR: ~ 10 ohmsSpin injection efficiency: ~ 8 %


51

Tunneling contact

MgOCo

graphene

Nonlocal MR: ~130 ohmsSpin injection efficiency: ~ 30 %


52

Spin flip during momentum scattering events:More momentum scattering, more spin relaxation.

s pts~ tp

J. Fabian, et al, Acta Phys. Slovaca (2007)R.J. Elliott, Phys. Rev. 96, 280 (1954)Josza, et al, Phys. Rev. B, 80, 241403(R) (2009)

Spin relaxation in graphene

53

More momentum scattering, less spin relaxation

s pts~ 1/tp

Momentum scattering can reduce this effect by randomizing the field

M. I. D'yakonov and V.I. Perel, Sov. Phys. Solid State, 13, 3023 (1972)


54

Elliot-Yafet

Vg -VD (V)

t s(p

s)

D(1

0-2

m2/s

)

T = 4K

ts~ tp ~ D


55

Dyakonov-Perel

Vg -VD (V)

t s(n

s)

D(1

0-2

m2/s

)

T = 4K

BLG

ts~ 1/tp ~ 1/D


56

1

s

1

sEY

1

sDP

KEY

DKDPD

SLG

BLG

KEY = 3.05 ± 0.35 (10-2 m2s-1)ns-1

KDP = -0.02 ± 0.10 (10-2 m2s-1)-1ns-1

KEY = 0.05 ± 0.01 (10-2 m2s-1) ns-1

KDP = 1.24 ± 0.09 (10-2 m2s-1)-1 ns-1


57

Dyakonov-PerelElliot-Yafet

Tombros, et al, Nature (2007)

Tombors, et al, PRL(2008)

Jozsa, et al, PRB (2009)

Han and Kawakami, PRL (2011)

~ 150 ps, impurity (EY)

Anisotropy (EY)

Linear scaling of λ & D (EY)

~1 ns, ts~ tp(D) (EY)

Han and Kawakami, PRL (2011)

Yang, et al, PRL (2011)

Up to 6 ns, ts~ 1/tp(1/D) (DP)

Up to 2 ns, ts~ 1/µ (DP)

Being under investigation: Random Rashba field Magnetic resonant scattering

Wang and Wu, et al, NJP (2012)

Kochan, et al, arXiv:1306.0230 (2013)


5858

D

Spin diffusion length

5959

Suspended graphene

Spin diffusion lengths 1-5 microns

Guimarães, et al, Nano Letters, 12, 3512-3517 (2012).Han, et al, Nano Letter, 12, 3443–3447 (2012).


6060

Guimarães, et al, PRL, 113, 086602 (2014)Drogeler, et al, Nano Letter, 14, 6050-6055 (2014)

Spin diffusion lengths >10 microns

Mobility > 1.0 m2/Vs


6161

Guimarães, et al, PRL, 113, 086602 (2014)

Anisotropy

6262

Guimarães, et al, PRL, 113, 086602 (2014)

Anisotropy

6363Dlubak, et al, Nature Physics, 8, 557–561 (2012)

An indirect method-- local MR measurement

Spin diffusion lengths >100 microns


6464

Spin lifetime Spin diffusion

lengths

Spin signals

Room

Temperature 0.5 - 2 ns > 10 µm 130 Ω

Low

Temperature 1 - 6 ns

> 10 µm

(> 100 µmindirect)

1 MΩ for local MR

Spin properties of graphene

6565


6666

Graphene

Large spin signal

Long spin lifetime

Long spin diffusion length

Easy to manipulate

Han, et al, Nature Nanotechnology, 9, 794-807 (2014)


6767

ON

OFF

(a) (b)

Yan, et al, Nat. Commun. 7, 13372 (2016).Dankert and Dash, Nat. Commun. 8, 16093 (2017).

Graphene/MoS2 channel

Graphene spin transistor

6868

Yan, et al, Nat. Commun. 7, 13372 (2016).Dankert and Dash, Nat. Commun. 8, 16093 (2017).

Graphene/MoS2 channel: gate tuning the channel and spin lifetimes

Graphene spin transistor

69

MoS2

Xiao, et al, PRL, 110, 066803 (2013)

70

Spin and Valley Hall in MoS2

Xiao, et al, PRL, 110, 066803 (2013)

71


Mak, et al, Science, 344, 1489-1492 (2014)

72


Mak, et al, Science, 344, 1489-1492 (2014)

73


74

Ising SC in MoS2 and NbSe2

Saito, Y., Nojima, T. & Iwasa, Y. Nat. Rev. Mater. 2, 16094, (2016)

75

Topological insulator

Topological insulators– Spin-Momentum locking

2D Topological insulator 3D Topological insulator

Qi & Zhang, Rev. Mod. Phys. 83, 1057 (2011)Hasan & Kane, Rev. Mod. Phys. 82, 3045 (2010)Yazyev, et al, Phys. Rev. Lett. 105, 266806 (2010).

7676

Spin ARPES: Hasan Group (Priceton University)


7777Li, et al, Nature Nanotechnology, 9 , 218–224 (2014).


7878

More information, please see the results ofJonker Group (Naval National Lab), KL Wang Group (UCLA) , Y. Chen Group (Purdue University) , etc


79


Shiomi, et al, PRL, 113, 196601 (2014)

80


81


Kim et al, Scientific Reports, 3, 3150 (2013)

82

Bulk states

Surfacestates

Temperature dependence


83


SmB6 BiSbSeTe

Shiomi, et al, PRL, 113, 196601 (2014)Xu, et al, Nature Comm., 5, 4566 (2014)

84

Outline

1. Superconductor Spin Valves

Large MR

Spin injection, Long spin lifetime

Large spin Hall effect

Spin-Triplet

85

Summary

2. Spin valves based on Quantum materials

石墨烯弱自旋-轨道耦合长自旋寿命

二硫化钼等自旋-谷

拓扑绝缘体自旋流的拓扑保护

© 2014 ICQM

下一节课: May 14th

Chapter 5: Spin transfer torque

课件下载：http://www.phy.pku.edu.cn/han_group/Teaching.htm

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Spin Valves - phy.pku.edu.cn