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Electronic tuning in CeCoIn5:a dirty job
Filip RonningFilip Ronning
Eric BauerEric BauerRyan BaumbachRyan BaumbachKris GofrykKris GofrykXin LuXin LuM.N. Ou (Owen)M.N. Ou (Owen)Tian ShangTian ShangJoe ThompsonJoe ThompsonPaul TobashPaul TobashVladamir SidorovVladamir SidorovJianxin ZhuJianxin Zhu ((LANLLANL))
S. StoykoS. StoykoA. Mar (A. Mar (U. AlbertaU. Alberta))
Hiroshi Yasuoka (Hiroshi Yasuoka (JAEAJAEA))Tuson Park (Tuson Park (SKKUSKKU))Zach Fisk (Zach Fisk (UC IrvineUC Irvine))
Los Alamos National Lab
Operated by Los Alamos National Security, LLC for NNSA
Outline
Motivation
“Dirt” in CeCoIn5
Dopants locally modify hybridization
Transition metal layers are NOT charge reservoir layers. (Sn vs. Pt doping)
Weak pair breaking effects in CeCoIn5 and quantifying it.
Normal state transport
Conclusions
(K. Gofryk, et al. PRL 109, 186402 (2012))
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Reducing Dimensionality
Increasing Bandw
idth
Incre
asing
T c10
0 x
CeIn3
CeMIn5
PuMGa5
Ce2MIn8
Tc = 0.2 K
Tc = 2.1 K
Tc = 18.5 K
Tc = 2.3 K
13 compounds in this family are
superconductors
NpPd5Al2Tc = 5 K
CeM2In7
Tc = 2.1 K
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2D
3D 2D
3D
Reducing dimensionality to maximize pairing
Monthoux , Pines, & Lonzarich, Nature ‘07
Enhance matching of (q,) to Q(q,) by reducing dimensionality
CeIn3 CeCoIn5
“Active” layer
“Buffer” layer
“Active” layer
• Prototypical strongly correlated system• Quantum Criticality• Heavy Fermion• dx2-y2 SC order parameter
Monthoux & Lonzarich, PRB ‘02
CeCoIn5
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Dirt as a microscope
(k)=?I. Mazin Nature ‘10
Heavy Fermion formationQuantum criticality
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Anderson / Abrikosov-Gorkov theories + corollaries
Anderson’s Theorem 1959
Abrikosov-Gorkov theory 1960
• For a SC order parameter which DOES NOT change sign
• Non-magnetic impurities are weakly pair breaking
• Magnetic impurities are strongly pair breaking
• For a SC order parameter which DOES change sign• Non-magnetic impurities are strongly pair breaking
1
2
S=0
1=2 ; S=0
S≠0
; S≠0 X
1
2
S=0
1≠2 ; S=0 X
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Debate on Fe-based superconductors
S. Onarii and H. Kontani, PRL ‘08Y. Nakajima, et al. PRB ‘10
• robustness to non-magnetic impurities may suggest that the Fe-based superconductors are conventional (s++)
See counter point
P. Hirschfeld, et al. Rep. Prog. Phys. ‘11
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Doping on the active layer: In-site Doping
R. Urbano, et al PRL ‘07
ElectronsHoles
• There are 2 effects • (1) Electronic tuning • (2) Pair breaking• EXAFS: Doping is preferentially on In(1) site
M. Daniel, et al PRL ‘05
CeMIn5
“Active” layer
“Buffer” layer
“Active” layer
Cd, Sn for In
Pt for Co
Sn for In
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What is the origin of the different doping behavior?
Cd, Hg, Sn for In
• Sn (electrons)• Cd, Hg (holes)• actual concentrations used from here on.
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Ce1
Co
Ce2
X
In1
• 2 x 2 x 2 supercell• doping = 0.025
0.4
0.2
0.0
PD
OS
-5 -4 -3 -2 -1 0 1 2 3 4 5 Energy (eV)
Sn 5p In 5p
0.6
0.4
0.2
0.0
PD
OS
-5 -4 -3 -2 -1 0 1 2 3 4 5
Energy (eV)
Cd 5p In 5p
• Cd has smaller bandwidth than In• Sn has larger bandwidth than In
The role of the dopant atoms
K. Gofryk, et al PRL ‘12
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Ce1
Co
Ce2
X
In1
JK = Vfc2(1/f+1/(2f+U))
30
20
10
0
PD
OS
-1.0 -0.5 0.0 0.5 1.0
Energy (eV)
Sn - doped Ce1 4f Ce2 4f
40
30
20
10
0
PD
OS
-1.0 -0.5 0.0 0.5 1.0
Energy (eV)
Cd - doped Ce1 4f Ce2 4f
• Cd locally decrease hybridization to Ce• Sn locally increases hybridization to Ce
The role of the dopant atoms
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Reversible electronic tuning
• JK decreases with hole doping (Cd and Hg)
• JK increases with electron doping (Sn and Pt)
• Doping creates an inhomogeneous internal field
JK
ElectronsHoles
R. Urbano, et al PRL ‘07
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Similarities in Cd and Hg tuningDFTPhase Diagrams
C. Booth, et al PRB ‘09
0.6
0.4
0.2
0.0
PD
OS
-5 -4 -3 -2 -1 0 1 2 3 4 5
Energy (eV)
Cd 5p Hg 6p In 5p
• Cd and Hg doped 115’s have nearly identical phase diagrams• DFT calculations with Cd and Hg impurity atoms give identical results
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CeIn3
CeMIn5
“Active” layer
“Buffer” layer
“Active” layer
Sn for In
Pt for Co
Electron dopants to distinguish buffer layers
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Sn vs Pt Tc suppression
• Impurity potential nearly identical for Sn and Pt dopants.• Implies screening length ≈ unit cell.
• No such thing as “buffer” layers in the 115s.• Tc → 0 @ 0 ~ 10 cm: Can we separate pair breaking and electronic tuning effects?
K. Gofryk, et al PRL ‘12
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Isolate pair breaking of holes using pressure
• Assume that dTc/Hg = dTc/dCd
L.D. Pham, et al. PRL ‘06
dTcmax/dCd = -5 K/Cd
• Cd doping reversible with pressure
L.D. Pham, et al. PRL ‘06
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Isolate pair breaking of electrons using co-doping
dTc/dSn = -13.3 K/Sn
• Tc initially increases with Hg co-doping
• SC suppressed, but AFM QC reversible with co-doping.
dTc/dPt = -11.2 K/Pt
• Pt and Sn doping reversible with Hg doping
K. Gofryk, et al PRL ‘12
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Comparison of pair breaking rates
dTc/dSn = -13.3 K/Sn
dTc/dPt = -11.2 K/Pt
dTc/dCd = -5 K/Cd
Rare Earths
Holes
Electrons
dTc/dR = -10 K/R
• Hole doping (AF droplets) is a significantly weaker pair breaker for superconductivity
• These are very weak suppressions, but how weak/strong is the impurity potential? Need 1/
C. Petrovic, et al. PRB ’02
J. Paglione, et al, Nat. Phys. ‘07
Hudson, et al. Nature ‘01
dTc/dZn ≈ 2 dTc/dNiCuprates:
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Extracting 1/ from resistivity
1/ = ne2/m* = /
= 190 – 550 um
T [K]
pure
Pt 0.09; Hg 0.025
Sn 0.09; Hg 0.025
R.J. Ormeno, et al. PRL ’02
S. Ozcan, et al, Eur. Lett. ‘03
W. Higemoto, et al. JPSJ ‘02
d(1/)/dSn = 330 K/Sn
d(1/)/dPt = 120 K/Pt
d(1/)/dCd = 830 K/Cd
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Comparison of pair breaking rates II
Impurity scattering for non-magnetic defects is remarkably weak compared with Abrikosov-Gorkov theory
K. Gofryk, et al PRL ‘12
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R. Movshovich, M. Jaime, J. D. Thompson, C. Petrovic, Z. Fisk, P. G. Pagliuso, and J. L. Sarrao, Phys. Rev. Lett. 86,
5152 (2001).
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Could CeCoIn5 be conventional?
NoVortex Lattice
Upper Critical Field
Specific Heat
Thermal conductivity
Neutron Resonance
Point Contact Andreev Reflection
NQR
Line Nodes!
dx2-y2!
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Spectrum of weak non-magnetic pair breakingexperiment theory• Conventional SC’s• Cuprate SC’s• Fe-based SC’s
• Short coherence length
• Anisotropic scattering
• Strong coupling
• Induced magnetic moments
M. Franz, et al. PRB ’02
G. Haran and H. Nagi, PRB ‘98
M.L. Kulic and O.V. Dolgov, PRB ’99
P. Monthoux and D. Pines, PRB ‘94• Coherence length = 5 nmR. Movshovich, et al. PRL ’01
• Multiband SC
• Cp/Tc = 4.5
• Induced moments with Cd doping
NMR: R. Urbano, et al. PRL ’07
• Spatial Inhomogeneity
E.D. Bauer, et al. PNAS ’11
C. Petrovic, et al. JPCM ’01
Thermal Conductivity
M. A. Tanatar, et al. PRL ‘05; G. Seyfarth, et al. PRL ‘08
Point Contact Spectroscopy P. Rourke, et al. PRL ‘05
• CeCoIn5
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Electronic tuning of CeCoIn5: transport• Sublinear transport
• unusual QCP• Mirrored by Cp data
• (Fisher-Langer)• The influence of disorder on the normal state is still poorly understood.• CeIrIn5 has a more “expected” response to disorder
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Electronic tuning of CeIrIn5: Cp
• Bulk Tc suppressed with doping. • QCP at slight hole doping.• Pt and Sn doping nearly identical
ElectronsHoles
T. Shang, et al unpublished
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CeIrIn5: low T transport summary
• Pt and Sn doping nearly identical
• “expected” behavior for a 2D AFM QCP.
T. Shang, et al unpublished
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Revisiting dimensionality in the 115 family
Monthoux , Pines, & Lonzarich, Nature ‘07
CePt2In7
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Possible future direction CeIn3
LDA Wannierization Tight Binding
Impurity potentials
SC instability
Model Hamiltonians (+U)
Doniach Diagram
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Conclusions Doping CeMIn5 has both a pair breaking effect and an electronic
tuning effect both of which influence Tc.
Similarity of Pt and Sn doping implies no “buffer” layer in CeMIn5.
Electron and hole doping locally modifies the hybridization and is reversible w.r.t. magnetism
Pair breaking is remarkably weak compared to Abrikosov-Gorkov theory
hole dopants are weaker than rare earth or electron dopants.
K. Gofryk, et al. PRL 109, 186402 (2012)