II Jornada científica NanoFrontMag - 12 de junio de 2018 - IMDEA Nanociencia Isabel Guillamón Universidad Autónoma de Madrid

1. Laboratorio de Bajas Temperaturas
Universidad Autónoma de Madrid
Unidad Asociada de Bajas Temperaturas y
Altos Campos Magnéticos (UAM-CSIC)
Imaging pnictide superconductors close to magnetic
instabilities via scanning tunneling spectroscopy
Isabel Guillamón

2. Iron-based superconductors
J. Paglione and R. L. Green, Nat. Phys. 6, 645-658 (2011)
FeAs plane
Magnetic order
Fe
As / Se
Li
Sr
La/Sr
O / F
Sc
11
111 122
1111
122*

3. Iron-based superconductors
Stripe-like AF order / orthorhombic structure
vv
vv
vv
A. Chubukov et al. Physics Today 68 (6), 46 (2015)

4. Iron-based superconductors
M. Rotter, et al., Angew. Chem., Int. Ed., 47, 7949 (2008)

5. Iron-based superconductors
s± pairing
Unconventional pairing
I. Mazin et al., Rep. Prog. Phys. 74, 124508 (2011)
P.J. Hirschfeld et al., C. R. Phys. 17, 197 (2016)

6. Iron-based superconductors
Cho et al. Sci. Adv. 2, 1600807 (2016)
©√
√√
√
√√

7. Disordered vortex lattice
BaFe1.8Co0.2As2
Yin,..,Hoffman, PRL 102 097002 (2009)
FeSe
Song et al, Science 332 1410 (2011)
Ba0.6K0.4Fe2As2
San et al, Nat Phys 7 325 (2011)
LiFeAs
Hanaguri et al, PRB 85 214505 (2012)
Fe(Se,Te)
Massee et al, Sci Adv 10 1126 (2015)
Fe(Se,Te)

8. Iron-based superconductors
vv
vv
vv
Superconductivity
Highest Tc appears in doped compounds
Only a few stoichiometric compounds are
superconductors
A. Chubukov et al. Physics Today 68 (6), 46 (2015)

9. Iron-based superconductors
vv
vv
vv
Superconductivity
Highest Tc appears in doped compounds
Only a few stoichiometric compounds are
superconductors
Intrinsic SC properties at
optimal Tc?
A. Chubukov et al. Physics Today 68 (6), 46 (2015)

10. Disordered vortex lattice
BaFe1.8Co0.2As2
Yin,..,Hoffman, PRL 102 097002 (2009)
FeSe
Song et al, Science 332 1410 (2011)
Ba0.6K0.4Fe2As2
San et al, Nat Phys 7 325 (2011)
LiFeAs
Hanaguri et al, PRB 85 214505 (2012)
Fe(Se,Te)
Massee et al, Sci Adv 10 1126 (2015)
Fe(Se,Te)
Intrinsic pinning mechanism?

11. Different approaches to these problems
Co-doped Ca122 CaKFe4As4P-substituted Ba122
A. Fente et al. PRB 97, 134501 (2018)
J. Benito et al., in preparation
V. Barrena et al., in preparationA. Fente et al. PRB 97, 014505 (2018)

12. Different approaches to these problems
Co-doped Ca122 CaKFe4As4P-substituted Ba122
A. Fente et al. PRB 97, 134501 (2018)
J. Benito et al., in preparation
V. Barrena et al., in preparationA. Fente et al. PRB 97, 014505 (2018)

13. 1144 Fe based superconductors

14. Fe
As / Se
Li
Sr
La/Sr
O / F
Sc
11
111 122
1111
122*
1144
CaKFe4As4
J. Paglione and R. L. Green, Nat. Phys. 6, 645-658 (2011) W.R. Meier et al., npj Quantum Materials 3, 5 (2018)
1144 Fe based superconductors

15. 1144
CaKFe4As4 W.R. Meier et al., npj Quantum Materials 3, 5 (2018)
Cho, Fente et al. Phys. Rev. B 95, 100502(R) 2017
1144 Fe based superconductors

16. 1144
CaKFe4As4 W.R. Meier et al., npj Quantum Materials 3, 5 (2018)
1144 Fe based superconductors

17. 1144
CaK(Fe1-xNix)4As4 W.R. Meier et al., npj Quantum Materials 3, 5 (2018)
1144 Fe based superconductors

18. Multigap superconductivity in CaKFe4As4
Vortex pinning in CaKFe4As4
Plan
Intrinsic HTc mechanism?
Intrinsic pinning mechanism?

19. Dilution refrigerator STM
Compact very low temperature STM with mechanically
driven horizontal linear positioning state
H. Suderow, I. Guillamón and S. Vieira
Rev Sci Inst, 033771, 82 (2011)
Dilution
Fridge
Superconducting Magnet
B < 22 T
Home-made electronics and mechanics.
Temperature down to 100 mK and magnetic field up to 22 T.
Mechanical pulling system to move the tip over the sample
Tip and sample
preparation methods

20. Current falicities at LBTUAM
• Dil fridge STM (15 mK)+ 5T-1T-1T (2×102)
• Dil fridge STM (30 mK)+ 9T (2×102)
• Dil fridge STM (7 mK)+ 9T(9×102)
• 4K-cryostat + 17 T (3)
• Dil fridge STM (7mK) + 17T (1.6×103)
• Dil fridge STM (7 mK) + 22T (2.2×103)
Very high magnetic field STM
Y.J. Song, et al., Review of Scientific
Instruments 81, 121101 (2010).

21. Current falicities at LBTUAM
• Dil fridge STM (15 mK)+ 5T-1T-1T (2×102)
• Dil fridge STM (30 mK)+ 9T (2×102)
• Dil fridge STM (7 mK)+ 9T(9×102)
• 4K-cryostat + 17 T (3)
• Dil fridge STM (7mK) + 17T (1.6×103)
• Dil fridge STM (7 mK) + 22T (2.2×103)
Very high magnetic field STM
Y.J. Song, et al., Review of Scientific
Instruments 81, 121101 (2010).

22. Very high magnetic field STM
Low Vibration Lab with floating floor
High magnetic field STM up to 22 T

23. Very high magnetic field STM
Low Vibration Lab with floating floor
High magnetic field STM up to 22 T

24. Very high magnetic field STM
High magnetic field STM up to 22 T
Low Vibration Lab with floating floor

25. Very high magnetic field STM
Reaching 22 T without a single quench!
Low Vibration Lab with floating floor
Bi2Pt
B. Wu, V. Barrena et al., in preparation

26. Very high magnetic field STM
High magnetic field STM (22 T, resistive magnets)
Low Vibration Lab with floating floor
Bi2Pt
F. Martín, R. Sánchez, et al. in preparation

27. Multigap superconductivity in CaKFe4As4
Vortex pinning in CaKFe4As4
Plan
Intrinsic HTc mechanism?
Intrinsic pinning mechanism?

28. STM in CaKFe4As4

29. STM in CaKFe4As4
gi
(a.u.)
0 10
D (meV)
Multiband
superconductor
∆ = ∆(k)
å -
=
i
i 2
i
2S
(k)ΔE
E
(E)N g
Cho, Fente et al. Phys. Rev. B 95, 100502(R) 2017

30. Two gap superconductivity
Collaboration with group of R. Prozorov (Ames)
Cho, Fente et al. Phys. Rev. B 95, 100502(R) 2017
Consistent
with s± pairing

31. Two gap superconductivity
Mou et al., PRL 117 277001 (2016)
abg
d

32. STM in CaKFe4As4
77 nm
A. Fente et al., PRB 97, 134501 (2018)

33. 2kF
STM/S in superconductors
Down to atomic scale… Quasiparticle interference: QPI
Charge waves by scattering
Real space conductance map
Energy, bias voltage
Wavevector
Fourier transform
L. Petersen et al. Phys. Rev. B, R6858, 57 (1998)
L. Simon, et al., J. Phys. Cond. Matt. 19 (2007) 355009

34. STM in CaKFe4As4
q
A. Fente et al., PRB 97, 134501 (2018)

35. STM in CaKFe4As4
q
A. Fente et al., PRB 97, 134501 (2018)

36. STM in CaKFe4As4
q
A. Fente et al., PRB 97, 134501 (2018)

37. STM in CaKFe4As4
Scale bars: 82 nm
A. Fente et al., PRB 97, 134501 (2018)

38. STM in CaKFe4As4
r
E
|∆|
~D2/EF
A. Fente et al., PRB 97, 134501 (2018)

39. STM in CaKFe4As4
C.-L. Song et al., Science 332, 1410 (2011)
L. Shan et al., Nature Physics 7, 325–331 (2011)
T. Hanaguri et al., Phys. Rev. B 85, 214505 (2012)
FeSe
(Ba0.6K0.4)Fe2As2
LiFeAs

40. STM in CaKFe4As4
A. Fente et al., PRB 97, 134501 (2018)

41. STM in CaKFe4As4
A. Fente et al., PRB 97, 134501 (2018)

42. STM in CaKFe4As4
4 T
0 meV
120 nm
A. Fente et al., PRB 97, 134501 (2018)

43. STM in CaKFe4As4
A. Fente et al., PRB 97, 134501 (2018)

44. Collaborators
W.R. Meier, S.L. Bud'ko, P.C. Canfield
Ames Laboratory and Iowa State University, USA
J. Benito, A. Fente, E. Herrera, V. Barrena, B. Wu, F. Martin, R. Sánchez
H. Suderow, S. Vieira
Laboratorio Bajas Temperaturas, Universidad Autónoma de Madrid
P. Walmsley, I.R. Fisher
Geballe Laboratory for Advance Materials
Stanford University

45. Imaging pnictide superconductors close to magnetic
instabilities via scanning tunneling spectroscopy
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