ECRYS – Electronic Crystals – Cargèse, August 25th, 2011. Vortex pinning : a
probe for nanoscale disorder in iron-‐based superconductors. Kees van der
Beek.
Vortex pinning : a probe for nanoscale disorder in iron-‐based superconductors Kees van der Beek Laboratoire des Solides Irradiés, Ecole Polytechnique, PALAISEAU, France
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
1
Collaborators • Sultan DEMIRDIŞ, Marcin KONCZYKOWSKI LSI, CNRS UMR 7642 & CEA/DSM/IRAMIS, Ecole Polytechnique, Palaiseau, France • Yanina FASANO, René CEJAS, Hernan PASTORIZA Laboratorio de Bajas Temperaturas, InsLtuto Balseiro, Centro Atomico Bariloche, San Carlos de Bariloche, ArgenLna • Dorothée COLSON, Florence ALBENQUE Service de Physique de l’Etat Condensé, CEA/DSM/IRAMIS, Gif sur YveSe, France •
Shigeru KASAHARA, Takahito TERASHIMA Research Center for Low Temperature and Materials Sciences, Kyoto University, Japan
•
Ryuji OKAZAKI, Takasada SHIBAUCHI, Yuji MATSUDA Department of Physics, Kyoto University, Kyoto, Japan
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
2
Iron-‐based superconductors Layered structure FeAs
FeSe
FeAs
LaFeAsO “1111”
BaFe2As2 “122”
PrFeAsO NdFeAsO SmFeAsO …
Ba(Fe,Co)2As2 BaFe2(As,P)2
Tc < 55 K
Tc < 42 K
FeSe
LiFeAs Tc < 20 K
Fe(Se,Te) Tc < 18K
From “To what extent pnictide superconductivity has been clarified: a progress report” Kenji Ishida, Yusuke Nakai, and Hideo Hosono, J. Phys. Soc. Japan 78, 062001 (2009).
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
3
IBS: Phase Diagram • Charge doped
• Isovalently doped
BaFe2(As1-‐xPx)2 Ba(Fe1-‐xCox)2As2
F. Rullier-Albenque, D. Colson, A. Forget, H. Alloul PRL 103, 057001 (2009)
S. Kasahara et al., Phys. Rev. B (2010)
• High sensi_vity to crystal structure details • Proximity to (an_-‐ferro)magne_sm ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
4
IBS: Electronic structure / gap • Mul_band Superconduc_vity • New paradigm for High Tc s.c. H. Ding et al., EPL 83, 47001 (2008)
Photoemission
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
5
IBS: Electronic structure / gap • Mul_band Superconduc_vity • New paradigm for High Tc s.c. H. Ding et al., EPL 83, 47001 (2008)
Photoemission
"Electron-‐like" sheets
"Hole-‐like" sheets
Μ
Μ
Γ
Μ
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
6
IBS: Electronic structure / gap • Mul_band Superconduc_vity • New paradigm for High Tc s.c. H. Ding et al., EPL 83, 47001 (2008)
Photoemission
• Proposal : AF coupling between "electron-‐like" and "hole-‐like" Fermi surface sheets "Electron-‐like" sheets
↓↑
-‐
-‐
↑↓
"Hole-‐like" sheets
↑↓
-‐
Sign of the phase of the superconduc_ng ↑↓ wave func_on
D.J. Mazin et al., Phys. Rev. Lett. 101, 057003 (2008);
K. Kuroki et al., Phys. Rev Lett. 101, 087004 (2008);
K. Kuroki et al., Phys. Rev B. 79, 224511 (2008);
+
-‐
" s± " – coupling
↑↓
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
7
IBS: Electronic structure / gap • Mul_band Superconduc_vity • New paradigm for High Tc s.c. H. Ding et al., EPL 83, 47001 (2008)
Photoemission
• Proposal : AF coupling between "electron-‐like" and "hole-‐like" Fermi surface sheets "Electron-‐like" sheets
↓↑
-‐
-‐
↑↓
"Hole-‐like" sheets
↑↓
-‐
Sign of the phase of the superconduc_ng ↑↓ wave func_on
D.J. Mazin et al., Phys. Rev. Lett. 101, 057003 (2008);
K. Kuroki et al., Phys. Rev Lett. 101, 087004 (2008);
K. Kuroki et al., Phys. Rev B. 79, 224511 (2008);
+
-‐
" s± " – coupling
↑↓ Role of disorder/impuri_es?
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
8
IBS: Electronic structure / gap • Mul_band Superconduc_vity • New paradigm for High Tc s.c. H. Ding et al., EPL 83, 47001 (2008)
Photoemission
• Proposal : AF coupling between "electron-‐like" and "hole-‐like" Fermi surface sheets "Electron-‐like" sheets
↓↑
-‐
-‐
↑↓
"Hole-‐like" sheets
↑↓
-‐
Sign of the phase of the superconduc_ng ↑↓ wave func_on
D.J. Mazin et al., Phys. Rev. Lett. 101, 057003 (2008);
K. Kuroki et al., Phys. Rev Lett. 101, 087004 (2008);
K. Kuroki et al., Phys. Rev B. 79, 224511 (2008);
+
-‐
" s± " – coupling
↑↓ Role of disorder/impuri_es?
9 – Electronic Crystals – Cargèse, August 011 Interband scamering = dECRYS estruc_ve interference = harmful , 2 5th, I2ntraband scamering = benign
Gap symmetry
Materials with similar structure do not have the same ground state K. Hashimoto, M. Yamashita, S. Kasahara, Y. Senshu, N. Nakata, S. Tonegawa, K. Ikada, A. Serafin, A. Carrington, T. Terashima, H. Ikeda, T. Shibauchi, and Y. Matsuda, Phys. Rev. B 81, 220501 (2010).
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
10
IBS : characterize the disorder defects nm-‐scale heterogeneity
vs
Intrinsic
impuri_es dopant atoms
Vortex pinning Extended defects pin differently than point-‐like defects
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
11
H
Crash-‐course on vor_ces π/2
Hc2
Etat state
normal Normal
π
3π/2 2ξ
j0
Mixed state
Etat mixte
λ
φ=0 2 Bc1 ns Bz(r)
j(r)
Hc1
Current density
Etat Meissner Meissner State
T
Tc
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
B (magn. flux density)
12
H
Crash-‐course on vor_ces π/2
Hc2
Etat state
normal Normal
π
3π/2 2ξ
j0
Mixed state
Etat mixte
φ=0 2 Bc1 ns Bz(r)
λ j(r)
Hc1
Current density
Etat Meissner Meissner State
T
Current-‐ voltage characteris_c F=j×B Lorentz force v = F/γ friction E=v×B Josephson relation
}
E = ρfj
where
Tc
B (magn. flux density)
E
flux flow
R
or V
ρf = B2/γ ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
j or I 13
H
Crash-‐course on vor_ces π/2
Hc2
Etat state
normal Normal
π
3π/2 2ξ
j0
Mixed state
Etat mixte
φ=0 2 Bc1 ns Bz(r)
λ j(r)
Hc1
Current density
Etat Meissner Meissner State
T
Current-‐ voltage characteris_c F=j×B Lorentz force v = F/γ friction E=v×B Josephson relation
}
E = ρfj
where
ρf =
B2/γ
Tc
B (magn. flux density)
E
flux flow
R
or V
flux creep
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
jc = Fp/B
j or I 14
Bimer decora_on of vor_ces in Ba(Fe0.9Co0.1)2As2 Field coil
B = 0.5 mT
Fe filament
10 µm Single crystal Ba(Fe0.9Co0.1)2As2 (D. Colson, F. Albenque)
Ba(Fe1-‐xCox)2As2 crystal
Single crystal Bi2Sr2CaCu2O8+δ (Y. Fasano)
Cf Eskildsen et al. (BD,SANS); Vinikov et al. (BD);
Inosov et al. (MFM, SANS); Kalisky et al.;
Luan et al. (scanning SQUID)
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
15
Jc of iron-‐based superconductors 1. Magneto-‐op_cal visualiza_on of B Ba(Fe0.9Co0.1)2As2
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
16
Jc of iron-‐based superconductors 1. Magneto-‐op_cal visualiza_on of B Ba(Fe0.9Co0.1)2As2
2. Flux density profiles: jc at low B 500
T = 10 K
B ( mT )
400
µ0 jc = 2
dB
dx
300
200
100
0 0
200
400
600
x ( !m )
800
1000
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
17
Jc of iron-‐based superconductors 1. Magneto-‐op_cal visualiza_on of B Ba(Fe0.9Co0.1)2As2 + + + + + + + +
3. Hall probe array magnetometry: hysteresis loops of local B, jc at higher B
2 109
Ba(Fe Co As) 10
1-x
x
T[K]
2
4.2 6 8 10 12 14 16
x=5% crystal #2 H || c
500
T = 10 K
B ( mT )
400
µ0 jc = 2
dB
dx
300
200
5 108 0
0 -5 108
-5 -1 109 -1.5 109
-10 -2
100
1 109
-1
0 B(T)
1
2
-2 109
0 0
200
400
600
x ( !m )
800
1000
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
18
j ( Am-2 )
2. Flux density profiles: jc at low B
dB/dx ( G / !m )
5
1.5 109
Vortex pinning and the cri_cal current density Strong pinning
Sparse extended defects (ni ξ -‐3)
• • •
•
modify the core and modify the screening current distribu_on Total force Fp = direct sum Σi fp,i of elementary pinning forces fp,i
Total force ~ 2nd moment of fp Fp = (np 〈fp2 〉/Vc)1/2
•
Vc = LcRc2
determined by
〈[u(Rc, 0) – u(0,0)] 2 〉1/2 = ξ
〈[u(0, Lc) – u(0,0)] 2 〉1/2 = ξ
• pins sufficiently effec_ve : Vc = Lca02 Yu. Ovchinnikov and B. Ivlev, PRB 43, 8024 (1991);
C.J. van der Beek et al PRB 66, 024523 (2002);
G. Blatter, V.B. Geshkenbein, J. Koopman, PRL 92, 067009 (2004).
Field-‐independent jc followed by e-B/B0
A.I. Larkin, Yu. Ovchinnikov, JETP 31, 784 (1970); J. Low. Temp. Phys. 34, 409 (1979). G. Blatter, M.V. Feigel'man, V.B. Geshkenbein, A.I. Larkin, and V.M. Vinokur, Rev. Mod. Phys. 66, 1125 (1994).
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
20
Jc of iron-‐based superconductors 1. Magneto-‐op_cal visualiza_on of B Ba(Fe0.9Co0.1)2As2 + + + + + + + +
3. Hall probe array magnetometry: hysteresis loops of local B, jc at higher B
2 109
Ba(Fe Co As) 10
1-x
x
T[K]
2
4.2 6 8 10 12 14 16
x=5% crystal #2 H || c
500
T = 10 K
B ( mT )
400
µ0 jc = 2
dB
dx
300
200
5 108 0
0 -5 108
-5 -1 109 -1.5 109
-10 -2
100
1 109
-1
0 B(T)
1
2
-2 109
0 0
200
400
600
x ( !m )
800
1000
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
21
j ( Am-2 )
2. Flux density profiles: jc at low B
dB/dx ( G / !m )
5
1.5 109
Jc of iron-‐based superconductors Ba(Fe0.925Co0.075)2As2 crystal #2.1 Critical current density vs applied magnetic field
jc(0; 5 K)
109
j ( Am-2 )
jc(0; 11 K)
0.5 2 109
Ba(Fe Co As)
jc(0; 17.5 K)
10
1-x
x
T[K]
2
4.2 6 8 10 12 14 16
x=5% crystal #2 H || c
5
8
5.0 K fit 3!108/B1/2 11.26 K fit 1!107/B1/2ı 17.5 K fit 2.8!07/B-1/2 0.01
1 109 5 108
0
0 -5 108
-5 -1 109
0.1
1
µ0Ha ( T )
-1.5 109
-10 -2
-1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
0 B(T)
1
2
-2 109
22
j ( Am-2 )
dB/dx ( G / !m )
10
1.5 109
Jc of iron-‐based superconductors Ba(Fe0.925Co0.075)2As2 crystal #2.1 Critical current density vs applied magnetic field
Yu. Ovchinnikov and B. Ivlev, PRB 43, 8024 (1991);
C.J. van der Beek et al PRB 66, 024523 (2002);
G. Blatter, V.B. Geshkenbein, J. Koopman, PRL 92, 067009 (2004).
jc(0; 5 K)
109
j ( Am-2 )
jc(0; 11 K)
0.5 2 109
Ba(Fe Co As)
jc(0; 17.5 K)
10
1-x
x
T[K]
2
4.2 6 8 10 12 14 16
x=5% crystal #2 H || c
5
8
5.0 K fit 3!108/B1/2 11.26 K fit 1!107/B1/2ı 17.5 K fit 2.8!07/B-1/2 0.01
1 109 5 108
0
0 -5 108
-5 -1 109
0.1
1
µ0Ha ( T )
Extended point-‐like defects with niξ3 MP@
_I_1P L
S. Demirdiş et al cond-mat 1106.6065v1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
38
Ba(Fe1-‐xCox)2As2 at low B : Pinning forces Hdec= 10 Oe
Tirr
Tdec
Tc
1P YRUWLFHV
D [
Tf
E [
[>MP@
Pinning force distribu_on at Tf
|fi| ~ 5×10-6 N/m
_I_1P L
1P YRUWLFHV
NB Newton’s 3rd law: Interac_on force must be balanced by pinning force
F
G
[>MP@
_I_1P L
Average Pinning force per vortex S. Demirdiş et al cond-mat 1106.6065v1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
39
Low B : Strong pinning by nm-‐scale disorder ε0 (T )
Spa_al inhomogeneity
ε0 ‒ Δε0
Tc
0.5 ε0
|fi| ~ 5×10-6 N/m
Average Pinning force per vortex
fp ~ 3×10-13 N
Pinning force of a single pin
Tc - δTc Distance between 2 pins ~ 60 nm
Nm-‐scale disorder
S. Demirdiş et al cond-mat 1106.6065v1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
40
Low B : Strong pinning by nm-‐scale disorder ε0 (T )
Spa_al inhomogeneity
ε0 ‒ Δε0
Tc
0.5 ε0
|fi| ~ 5×10-6 N/m
Average Pinning force per vortex
fp ~ 3×10-13 N
Pinning force of a single pin
Tc - δTc Distance between 2 pins ~ 60 nm
Nm-‐scale disorder Cri_cal current density ?
S. Demirdiş et al cond-mat 1106.6065v1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
41
Low B : Strong pinning by nm-‐scale disorder ε0 (T )
0.05 ε0
Spa_al inhomogeneity
ε0 ‒ Δε0
Tc
0.5 ε0
|fi| ~ 5×10-6 N/m
Average Pinning force per vortex
fp ~ 3×10-13 N
Pinning force of a single pin
Nm-‐scale disorder
Tc - δTc Distance between 2 pins ~ 60 nm
4 109 3.5 109
Cri_cal current density ?
(a)
(b)
B = 30 mT
25
x = 0.075
jc ( Am-2 )
3 109
109
2.5 109
20
2 109
5K
1 109
Up ~ ∆ε0 = 0.05 ε0
108
5 108 0
Tc ( K )
1.5 109
11 K
x = 0.075 #2.1 x = 0.1 #1 0
5
10
17.5 K 15
T(K)
20
25
0.01
1 0.1 µ0Ha ( T ) et al S. Demirdiş
15
10
cond-mat 1106.6065v1
ECRYS –FIG. Electronic Crystals – Cargèse, August 25th, 2: (Color online) (a) Temperature of2011 the low-field critical current density in Ba(Fe0.925 Co0.075 )2 As2 crystal #2 and Ba(Fe0.9 Co0.1 )2 As2 crystal #1 . Error bars represent the dis-
42
5 6 108
#1 #2 #3
Low B : Strong pinning by nm-‐scale disorder ε0 (T )
0.05 ε0
Spa_al inhomogeneity
ε0 ‒ Δε0
Tc
0.5 ε0
|fi| ~ 5×10-6 N/m
Average Pinning force per vortex
fp ~ 3×10-13 N
Pinning force of a single pin
Nm-‐scale disorder
Tc - δTc Distance between 2 pins ~ 60 nm
4 109 3.5 109
Cri_cal current density ?
(a)
(b)
B = 30 mT
jc ( Am-2 )
3 109
109
2.5 109
25
x = 0.075
Gap maps
20
2 109
5K
1 109
Up ~ ∆ε0 = 0.05 ε0
108
5 108 0
Tc ( K )
1.5 109
11 K
x = 0.075 #2.1 x = 0.1 #1 0
5
10
17.5 K 15
T(K)
20
25
0.01
F. Massee
1 0.1 etµal., H (Phys. T ) Rev. 0 a
15
10
B 79, 220517 (2009)
ECRYS –FIG. Electronic Crystals – Cargèse, August 25th, 2: (Color online) (a) Temperature of2011 the low-field critical current density in Ba(Fe0.925 Co0.075 )2 As2 crystal #2 and Ba(Fe0.9 Co0.1 )2 As2 crystal #1 . Error bars represent the dis-
43
5 6 108
#1 #2 #3
Jc of iron-‐based superconductors Mesures locales du courant cri_que jc • 2 contribu_ons: Extended defects Small B Point-‐like impuri_es Larger B
jc(0; 5 K)
109
j ( Am-2 )
jc(0; 11 K)
jc(0; 17.5 K)
10
0.5
8
x
2
4.2 6 8 10 12 14 16
x=5% crystal #2 H || c
1.5 109 1 109 5 108
0
0 -5 108
-5 -1 109
0.1
1
µ0Ha ( T )
-1.5 109
-10 -2
-1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
0 B(T)
1
2
-2 109
44
j ( Am-2 )
5.0 K fit 3!108/B1/2 11.26 K fit 1!107/B1/2ı 17.5 K fit 2.8!07/B-1/2 0.01
1-x
T[K]
5
dB/dx ( G / !m )
10
2 109
Ba(Fe Co As)
3 >> 1 High Mesures B : origin olf ocales weak ``collec_ve’’ p inning n ξ p j du courant cri_que
c
Two main clues:
• Magnitude of jc
he ohe
109
4
(b)
3 2
10
1 0 -1
-0.5
0
0.5
1
PrFeAsO1-y NdFeAsO0.9F0.1 Ba0.45K0.55Fe2As2
10
0.2
0.4
2
4.2 6 8 10 12 14 16
x=5% crystal #2 H || c
1.5 109 1 109 5 108
0
0 -5 108
-5
-1.5 109
-10
0.6
T / Tc
FIG. 3: tion jccoll
x
-1 109
Ba0.72K0.28Fe2As2 [35] Ba(Fe0.9Co0.1)2As2 [30]
0
1-x
T[K]
5
# charges / u.c.
8
2 109
Ba(Fe Co As)
dB/dx ( G / !m )
,
jccoll ( Am-2 )
(a)
0.8
1
-2
-1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011 (Color online) (a) Collective pinning contribuin the charge-doped compounds PrFeAsO1−y ,
0 B(T)
1
2
-2 109
45
j ( Am-2 )
of y,
jccoll ( 109 Am-2 )
C.J. van der Beek et al., PRL 105, 267002 (2010)
α
4) ny. r2 mi va of nt in
3
• Temperature dependence of jc
3 >> 1 High Mesures B : origin olf ocales weak ``collec_ve’’ p inning n ξ p j du courant cri_que
c
Two main clues:
• Magnitude of jc • Temperature dependence of jc
• Local varia_ons of Tc • Charge redistribu_on • Reduc_on of the pairing poten_al V
fp = (Bc2/µ0) Dv3/ξ ~ ε0 (Dv/ξ)3
p p
p
G. Blatter, M.V. Feigel'man, V.B. Geshkenbein, A.I. Larkin, and V.M.Vinokur, Rev. Mod. Phys. 66, 1125 (1994).
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
46
3 >> 1 High Mesures B : origin olf ocales weak ``collec_ve’’ p inning n ξ p j du courant cri_que
c
Two main clues:
• Magnitude of jc • Temperature dependence of jc
• Local varia_ons of Tc • Charge redistribu_on • Reduc_on of the pairing poten_al V
• Quasipar_cle scamering (δl or δκ) • ξeff = (ξ0l)1/2
fp = (Bc2/µ0) Dv3/ξ ~ ε0 (Dv/ξ)3
p p
p
G. Blatter, M.V. Feigel'man, V.B. Geshkenbein, A.I. Larkin, and V.M.Vinokur, Rev. Mod. Phys. 66, 1125 (1994).
E.V. Thuneberg, J. Kürkijärvi, D. Rainer, PRL 48, 1853 (1982).
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
47
High B : origin of weak pinning Mesures locales du c``collec_ve’’ ourant cri_que j c
Two main clues:
• Magnitude of jc : pinning by dopant atoms reproduce this for the correct nd 3
• T-‐dependence of jc : reproduced by pinning due to quasi-‐par_cle scamering
he ohe
3 2
10
1 0 -1
-0.5
0
0.5
1
PrFeAsO1-y NdFeAsO0.9F0.1 Ba0.45K0.55Fe2As2
10
0.2
0.4
2
4.2 6 8 10 12 14 16
x=5% crystal #2 H || c
1.5 109 1 109 5 108
0
0 -5 108
-5
-1.5 109
-10
0.6
T / Tc
FIG. 3: tion jccoll
x
-1 109
Ba0.72K0.28Fe2As2 [35] Ba(Fe0.9Co0.1)2As2 [30]
0
1-x
T[K]
5
# charges / u.c.
8
2 109
Ba(Fe Co As)
dB/dx ( G / !m )
109
4
p
(b)
0.8
1
-2
-1
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011 (Color online) (a) Collective pinning contribuin the charge-doped compounds PrFeAsO1−y ,
0 B(T)
1
2
-2 109
48
j ( Am-2 )
of y,
,
jccoll ( Am-2 )
(a)
α
4) ny. r2 mi va of nt in
jccoll ( 109 Am-2 )
C.J. van der Beek et al., PRL 105, 267002 (2010)
Scattering parameters from jc of IBS compound
impurity
PrFeAsO0.9 (vacancy) NdFeAsO0.9F0.1 (F) Ba(Fe0.9Co0.1)2As2 ( Co ) Ba0.72K0.28Fe2As2 ( K ) Ba0.6K0.4Fe2As2 (K) Ba0.45K0.55Fe2As2 ( K ) kF ~ 0.3 Å-1
np (nm-3) 1.5 1.5 2 2.8 4 5.5
sin δ0 = 2-1/2 kFDv
Dv (Å) 1.46 0.9 0.9 0.7 0.8 0.7
0.3(2) 0.2 0.17 0.1(4) 0.2 0.2
l ( nm ) 10 25 20 23 10 12
C.J. van der Beek et al., PRL 105, 267002 (2010)
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
49
Scattering parameters from jc of IBS compound
impurity
PrFeAsO0.9 (vacancy) NdFeAsO0.9F0.1 (F) Ba(Fe0.9Co0.1)2As2 ( Co ) Ba0.72K0.28Fe2As2 ( K ) Ba0.6K0.4Fe2As2 (K) Ba0.45K0.55Fe2As2 ( K )
np (nm-3) 1.5 1.5 2 2.8 4 5.5
Dv (Å)
sin δ0 = 2-1/2 kFDv
1.46 0.9 0.9 0.7 0.8 0.7
0.3(2) 0.2 0.17 0.1(4) 0.2 0.2
l ( nm ) 10 25 20 23 10 12
Kontani and S. Onari, Phys. Rev. Lett. 104, 157001 (2010).
δTc ~ 100 – 200 %
V. Mishra et al., Phys. Rev. B 79, 094512(2009).
δTc ~ 50 %
Tc/Tc0
kF ~ 0.3 Å-1
Γ = [nd/πNn(0)] sin δ0
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
50
Summary • Two contribu_ons to flux pinning in IBS • Strong pinning (extended defects) niξ3 > 1 -‐ QP scamering in the vortex core -‐ Extract scamering parameters, problema_c for s± C.J. van der Beek et al., PRL 105, 267002 (2010); PRB 81, 174517 (2010). S. Demirdiş et al cond-mat 1106.6065v1 ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
51
Hystere_c magne_za_on loops for different IBS 1 Ba0.45K0.55Fe2As2 10
10
0.5
jccoll+jcs(0) -2
j ( Am )
NdFeAsO0.9F0.1 BaFe2(As0.67P0.33)2 Hon(PrFeAsO)
0
108
-0.5
-1
109
c
Bs / Bs( 0 )
PrFeAsO1-y
jccoll+jc
jcs(0)
C.J. van der Beek et al., PRL 105, 267002 (2010)
-2
-1.5
-1
-0.5
0
0.5
1
1.5
107
2
µ0Ha ( T )
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
FIG. 1: (Color online) Normalized hysteresis loops of the
52
FIG. 2: (Color on
the sur-
2 Cri_cal current density for different IBS
10
10
jccoll+jcs(0)
0.5
(Ba,K)Fe2As2
jccoll
-2
j ( Am )
jccoll+jcs(0)
jc
109
c
Hon 0.5 s
108
jc (0)
Ba(Fe,Co)2As2
jccoll
NdFeAs(O,F)
BaFe2(As1-xPx)2
Ba0.45K0.55Fe2As2 Ba0.6K0.4Fe2As2 [36 ]
10
Hon
jccoll
PrFeAsO1-y NdFeAsO0.9F0.1
7
PrFeAsO1-‐y
coll
Ba(Fe0.9Co0.1)2As2 [34 ]
0.01
x=0.23 x=0.33 x=0.49
0.1
B(T)
BaFe2(As,P)2 1 C.J. van der Beek et al., PRL 105, 267002 (2010)
ECRYS – Electronic – Cargèse, August 25th, FIG. 2: (Color online) Critical currentCrystals density as function of2011 magnetic flux density for PrFeAsO1−y (✷), NdFeAsO0.9 F0.1 (◦), Ba(Fe Co ) As (�) [35], Ba K Fe As ( , �), and
53
PrFeAsO1-‐y
µ0 jc = 2
dB
dx
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
54
Local measurement of jc PrFeAsO1-‐y
Hall probe arrays µ0 jc = 2
dB
dx
Magneto-‐op_cal visualisa_on ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
55
Local measurement of jc Low field
• two contribu_ons: -‐ -‐
Extended defects Point-‐like Impuri_es
Higher field
ECRYS – Electronic Crystals – Cargèse, August 25th, 2011
56