domain walls at the sdw endpoint of (tmtsf) 2 pf 6 under pressure
DESCRIPTION
SDW. M(SC). SDW. M(SC). SDW. M(SC). Domain walls at the SDW endpoint of (TMTSF) 2 PF 6 under pressure. C.Pasquier , Laboratoire de Physique des Solides, Orsay S. Brazovskii LPTMS, Orsay Acknowledgments: P. Grigoriev. N. Kang, B.Salameh , P. Auban-Senzier, D.Jérome. Outline. - PowerPoint PPT PresentationTRANSCRIPT
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Domain walls at the SDW endpoint of (TMTSF)2PF6 under pressure
C.Pasquier,
Laboratoire de Physique des Solides, OrsayS. Brazovskii
LPTMS, OrsayAcknowledgments: P. Grigoriev
SDW
SDW
SDW M(SC)
M(SC)
N. Kang, B.Salameh, P. Auban-Senzier, D.Jérome
M(SC)
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SCSC SCSDWSDWSDW
Outline
• Superconductivity at the border of density wave states
• The case of (TMTSF)2ReO4
• Phase separation in (TMTSF)2PF6
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SCSC SCSDWSDWSDW
SC/CDW proximity
Superconductivity at the end point of a charge density wave state
in organic and inorganic systems
SC
CDW
L.Brossard et al , PRB (1990)
A. F. Kusmartseva et al., PRL 103, 236401 (2009)
TiSe2
Per2 [Au(mnt)2]
D. Graf et al, EPL, 85 27009 (2009)
1T-TaS2
Tc,max 6-8K
TTF [Ni(dmit)2]2
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SCSC SCSDWSDWSDW
SC/(SDW or AF) proximity
S. Nandi et al., PRL 104, 057006 (2010).
Superconductivity at the end point of a spin density
wave (or AF) state in organic and inorganic
systems
-(BEDT-TTF)2X
(TMTTF)2X & (TMTSF)2X
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SCSC SCSDWSDWSDW
SC/DW proximity
Superconductivity at the end point of density wave is therefore a common feature in unconventional superconductivity.
How does SC emerge from a density wave state ?
We will focus on a 1D organic systems, essentially (TMTSF)2PF6
It appears that there is a phase coexistence with the formation of domains and not ‘stripes’.
We have to be careful and check that such phase coexistence is not due to structural transition like in (TMTSF)2ReO4: what happens in this case ?
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2ReO4
Moret R., Pouget J.-P., Comes R. and Bechgaard K., Phys.Rev.Lett., 49 (1982) 1008Parkin S.S.P. Jérome D. and Bechgaard K., Mol.Cryst.Liq.Cryst., 79 (1981) 213
SC at low Temperature above 8kbar
a
b
cInsulator
Metal
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2ReO4
Self- organisation along a
6 7 8 9 1020
40
60
80
100
120
140
160
180
200
ANISOTROPIE (b/a)
Pression (kbar)
Te
mp
éra
ture
(K
)
00.30000.60000.90001.2001.5001.8002.1002.4002.7003.0003.3003.6003.9004.2004.5004.8005.1005.4005.7006.000
6 7 8 9 10 1120
40
60
80
100
120
140
160
180
200
Pression (kbar)
Te
mp
éra
ture
(K
)
00.30000.60000.90001.2001.5001.8002.1002.4002.7003.0003.3003.6003.9004.2004.5004.8005.1005.4005.7006.000
ANISOTROPIE (c/a)
6 7 8 9 1020
40
60
80
100
120
140
160
180
200
Pression (kbar)
Tem
péra
ture
(K
)
00.30000.60000.90001.2001.5001.8002.1002.4002.7003.0003.3003.6003.9004.2004.5004.8005.1005.4005.7006.000
ANISOTROPIE (c/b)
C.Colin et al., EPL, 75, 301 (2006)
(log scale) (log scale)
(log scale)
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2ReO4
(2a,2c)
(a,2c)
Metal Semiconductor
2 possible orientations for each anion
Simple model : anisotropic Ising model
Pseudospin :
|+> if lattice parameter = 2a
|-> if lattice parameter = a
anisotropic interactions between spins anisotropic interactions between chains
Filaments or anisotropic bubbles oriented along a
Onsager (1941)
Pouget, Ravy,…
a
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
c-axis
a-axis
b-axis
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
-4 -2 0 2 4
2
3321mK
dV/d
I (k
)
(A)
P: 7.1kbar
87mK
SC along c
PHASE A : SC visible along c* only!
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
c =0 at low TDouble transition in b which disappears when P increases.
Clear non-linearities as a function of currentSome features are field independent
PHASE B : SC visible along c* and b’!
0 1 2 3
0
2
4
6
8
0
10
20
0
50
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.61
2
3
4
5
c
cm)
Temperature (K)
(b)
b
a
P: 8.0 kbar
b (m
cm
c
(a)
am
cm
H (G)
171161134105765038
dV/d
I(a.
u.)
(mA)
T: 360mK
0
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
Non linearities at zero bias persist up to high fields.
They appear with SC at low pressure and disappear for PPc0
PHASE A: 7.5kbar
PHASE B: 8kbar
H
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
Double transition in a which disappears when P increases.
PHASE C : SC visible along c*, b’ and a!
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
From bubbles to slabs by adjusting hydrostatic pressure
Josephson junctionsTunnel junctions
a
c b
SDW
SC
SDW
SDW SDWSDW
SCSC SC
SDW
SC
SDW
SC
SC
SC
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
How to understand this texture evolution ?
Why SC does appear first along c (the worst conducting direction!!!!) ?
Many theories have been developed for cuprates… …..but only one theory seems to fit our data
Soliton model :Existence of soliton domain walls (metallic) perpendicular to a- axisand expected peak of the anisotropy b,c / a at the DW / Metal transition
S. Brazovskii, L.P. Gorkov and A.G. Lebed, JETP 56 (1982) 683L.P.Gorkov, P.D.Grigoriev, EPL 71,425 (2005); PRB, 75, R20507 (2007)
a
c b
SDW
SC
SDW
SDW SDWSDW
SCSC SC
SDW
SC
SDW
SC
SC
See also experiments by Lee et al (PRL 2002,PRL 2005)
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
An image with the hands of the soliton model : how do metal (SC) emerge from a DW
Ecreation of a soliton < SDW gap
N. Kang et al. PRB (2010)
Journées labo, 7 Octobre 2010
SDW
Low pressure:Homogeneous SDW
SDW
Phases B and C: Bands in the SDW gap
‘soliton phase’
SC
SDW
Phase A: Midgap state in SDW gap
High pressure : SC homogeneous phase
SC
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
We believe that the deep in dV/dI characteristics is related to this particular band structure (as we are doing tunneling experiments!)
SDW
Low pressure:Homogeneous SDW
SDW
Phases B and C: Bands in the SDW gap
‘soliton phase’
SC
SDW
Phase A: Midgap state in SDW gap
High pressure : SC homogeneous phase
SC
PHASE B: 8kbar
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
a
c b
SDW
SC
SDW
SDW SDWSDW
SCSC SC
SDW
SC
SDW
SC
SC
? Why c first ???
bbaa ktktE cos2cos2)( 0k
),4/1,2/1( cnesting qQ
),2/1,2/1(tan cdards qQ
J.P.Pouget, S.Ravy, Synth. Metals 85,1523 (1997)T.Takahashi et al, JPSJ 55,1364 (1986)
Experiments :
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SCSC SCSDWSDWSDW
Phase coexistence in (TMTSF)2PF6
a
c b
SDW
SC
SDW
SDW SDWSDW
SCSC SC
SDW
SC
SDW
SC
SC
Why c first ???
ccbb ktktE cos22cos'2)(' k
governs the evolution from SDW to metal)(')(')( kQkk EEE nestinganti
= deviation from nesting
As qb ¼, the term in kb is small, the term in kc is dominant.So ‘’’’’everything’’’’’ is fixed along ka and kb but not kc.
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SCSC SCSDWSDWSDW
Conclusion
We have followed experimentally the evolution of the Metal (SC) concentration in the SDW matrix in (TMTSF)2PF6:
bubbles - filaments - slabs evolution
This evolution is understandable within a ‘soliton model’
Future : Is this evolution observable in other 1D systems or other materials with SDW/SC competition at the mesoscopic scale?
Is it related to the particular Fermi surface of (TMTSF)2PF6 whereelectrons for SC and SDW come from the same band.
Same features for CDW/SC competition ?
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SCSC SCSDWSDWSDW
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SCSC SCSDWSDWSDWCargese August 18, 2011
The ‘green flash’ spot ?