a new high temperature superconductor pucoga5 and its implications
DESCRIPTION
A New High Temperature Superconductor PuCoGa5 and its Implications. Yunkyu Bang (Chonnam National University) Collaborators (LANL) : A.V. Balatsky, M. Graf (theory) N. Curro , J.D. Thompson, J. Sarrao, E. Bauer (experiment). Summary: PuCoGa5 is an unconventional SC (d-wave) - PowerPoint PPT PresentationTRANSCRIPT
A New High Temperature Superconductor PuCoGa5 and its Implications
Yunkyu Bang (Chonnam National University)
Collaborators (LANL) : A.V. Balatsky, M. Graf (theory)
N. Curro , J.D. Thompson, J. Sarrao, E. Bauer (experiment)
Summary:
1. PuCoGa5 is an unconventional SC (d-wave)
2. Magnetic fluctuations (AFM) mediated pairing
3. This material is a strongly correlated f-electron metal (HF)
4. Tc 20 K , intermediate between HF and HTSC
5. Pseudo gap energy 20 K , intermediate between HF and HTSC
Q: Can we extend the results of PuCoGa5 to HTSC ?
A: ?
5 10 15 20
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
5 10 15 200
100
200
300
400
500
C/T
(m
J/m
ol K
2 )
T (K)
4
T (K)
PuCoGa5 Superconductivity
perfect diamagnetism (small Meissner effect) and zero resistivity below Tc=18.5K
C/T bulk superconductivity assuming BCS weak coupling, C/Tc=1.43 =77 mJ/molK2
J. L. Sarrao et al., Nature 420, 297 (2002)
Important questions:
1. Pairing symmetry
Conventional or Unconventioanl ? (s-wave or non s-wave ?)
2. Pairing glue
phonons or non-phonons ?
If phonon mediated s-wave SC (Θ D 240 K) not interesting
If unconventional SC very exciting material (why ?)
Unconventional SC : Tc ~ 1K in Heavy Fermion SC
Tc ~ 100K in cuprates HTSC
Long standing question : Why such a big difference by two orders ?
PuCoGa5 might bridge the missing gap
1. Tc ~ 20K
2. the highest Tc among the f-electron based compounds;
Previous record was ~2 K in CeCoIn5
3. γ ~70-90 mJ/mol K2 strong correlation (HF )
Isostructural to CeM(Co,Rh,Ir)In5
PuCoGa5CeCoIn5
Neutron scattering data (P=0) by W. Bao(quasi 2D AFM fluctuations)
Phases in CeRhIn5 under PressureT. Mito et al.. PRB 63, 220507 (2001)
Pressure up
Kawasaki et al, PRL 91 (2003)
Heeger et al, PRL 84 (2001)
2 4 6 8 10
100
150
200
250
300
1 100
200
400
600
800
C/T = 0 - ALogT
(B = 5 T)CeCoIn5
C/T
(m
J m
ole-1
K-2
)
T (K)
CeCoIn5
C/T = 0 - BLogT
C
/T (
mJ
mol
e-1 K
-2)
T (K)
0 5 10 15 200.0
5.0x10-4
1.0x10-3
1.5x10-3 CeCoIn5
R ()
T (K)
(R-R0)=AT1.06
3<T<18 K
CeCoIn5 (Tc=2.3K) : Cp, and 1/T1
T1.06 (to 15-20 K)
above Tc=2.3 K, C/T –lnT (to 8K) and Indicating near QC (2D AFM)
CeCoIn5
G.-q. Zheng et al., PRL 86, 4664 (2001)
~T3 ;lines of node
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
0 1 2 30
1
2
CeCoIn5
(C
-CS
ch)/T (J/
mol
K2 )
T (K)
T (K)
C/T
(J/
mol
K2 )
unconventional superconductivity (power laws in C/T, and 1/T1) with Tc of2.3 K
strong 4-fold modulation of for H in the a-b plane
consistent with dx2-y2 symmetry (K. Izawa et al. PRL 85, 057002 (2001))
Hc2(0) exceeds Pauli limit by a factor of two, as in PuCoGa5
Unconventional Superconductivity in CeCoIn5
4-fold line nodes;
D-wave Movshovich et al PRL 2001
CeCoIn5 and Relationship to CeRhIn5
0 20 40 600
1
2
3
4
5
6
TPG
CeCoIn5
(P + 16 kbar)T
N
CeRhIn5
T (
K)
P (kbar)
Tc
CeIn3
NFL
CePd2Si2
N D Mathur et al, Nature, vol393, p39,1998
Sidorov et al, PRL 89 (2002)
x
SC
AF
NFL
FL
QCP
HF SC (AFM)
Magnetic Origin
(1) Phonon mediated superconductivity
as in A-15 compound (eg. Nb3Sn)
D240 K from fitting of C(T) for T > Tc
McMillan Tc formula : * =0.1 and =0.5 or 1.0 Tc= 2.4-13.8K
(2) Spin fluctuations mediated superconductivity
Xrystal structure isostructural to CeMIn5
Pu 5-f-electrons FS
(band calculations by I. Opahle et al, PRL 90, 157001 (2003) and T. Maehira et al, PRL, 90, 207007 (2003).)
Pairing Glue ?
Strategy : fit exp(T) with candidate boson scattering for its functionalform as well as the magnitude of exp(T)
best boson, ch, and Tc
saturation
T4/3 ~
Resistivity fitting with two models: phonon and spin fluctuations
Spectral density of Boson
Phonon model :
Fitting with Experiment
Einstein phonon
Shunted resister model :
Phonon scattering is very unlikely to explain exp (T) .
Spin fluctuations model :
Fitting with Experiment
Bang et al PRB 70 (2004)
Energy Scale Tuning in CeCoIn5 & AMGa5 (J Sarrao et al, J Phys: Cond Matt 15, s 2275 (2003))
0.0 0.2 0.4 0.6 0.8 1.0 1.20.0
0.2
0.4
0.6
0.8
1.0
1.2
(T
) (T
ma
x)T/Tmax
CeCoIn5AMGa5
(A=U, Pu; M=Co, Rh)
0 200 400 600 8000.00
0.02
0.04
-1 (
mol
-K/m
J)
Tmax (K)
Tsf Tmax 1
• common “S”-shape of (T) curve suggests role of spin fluctuations
• Increase in bandwidth sf Tc
• no SC in UCoGa5 is due to a large imp effect
0
50
100
150
200
250
300
0 100 200 3000
5
10
15
20
UCoGa5
PuCoGa5
(
cm)
T (K)
CeCoIn5
Magnetic fluc. = common scattering source for 1K to 20K of Tc
Pairing Symmetry ?
Symmetry Probes :
C(T)/T
Penetration depth ((T))
NMR 1/T1 Density of states
Thermal conductance (κ(T))
Tunneling
Josephson Tunneling : direct phase probe
~T3 ;lines of node
1/T1 , the best probe to see the dos at low temp
~T3
Impurity state
Zheng et al, PRL 86 (2001)
Mito et al, PRB 63 (2001)
Fig.8. The normalized Knight shifts K(T)/Kn.
Solid lines are theoretical calculations for S-wave with varying concentrations of magnetic impurities of unitary limit (c=0). The normalized experimental data are with (blue stars) and without (red circles) subtraction of a constant part.
Figure 5. Normalized Knight shift K(T)/Kn.
Red circles are 59Co data. Solid lines are
theoretical calculations for D-wave with varying
concentrations of unitary impurities (c=0).
Figure 4. Normalized 1/T1. Red circles are 59Co data. Solid lines are theoretical calculations for D-wave with varying concentrations of unitary impurities (c=0).
Figure 7. Normalized 1/T1. Red circles are 59Co
data. Solid lines are theoretical calculations for S-
wave with varying concentrations of magnetic
impurities of unitary limit (c=0).
(b) (T1T) -1 /(T1T) -10 versus T/Tc for PuCoGa5, as well as for the
unconventional superconductors YBa2Cu3O7, (Tc = 92 K)7 and CeCoIn5, (Tc=2.3 K)27 and the s-wave superconductors Al (Tc=1.178 K)8, and MgB2, (Tc=39.2 K)11. The normalization constant (T1T)-1 0 is given by the value of (T1T)-1 at 1.25Tc (see Methods).
Unconventional d-wave SC
Curro et al, Nature 434, 2005
Curro et al, Nature 434, 2005
0
5
10
15
20
B
an
dw
idth
(e
V)
Atomic Number
5d
4d
3d
5f4f
Schematic Evolution of Bandwidths across the Period Table
Electrons in the unfilled shell become progressively more localized in the sequence 5d 4d 3d 5f 4f suggests an alternative way to ‘organize’ the periodic table
From J.D. Thompson
Onuki et al, 2005
PuRhGa5
=8.5K
20 /Tc = 5 for PuRhGa5
20 /Tc = 8 for PuCoGa5
Very similar to underdoped HTC cuprates
Pseudo-Gap in PuRhGa5
Sakai et al 2005
PuCoGa5: PuRhGa5
2/Tc ~8, 2/Tc ~5
C/Tc ~ 90mJ/molK2 , ~ 45 mJ/molK2
1/T1T QC QD
Conclusion:
1. Unconventional SC from 1K to 20 K may have an unifying mechanism of the magnetic fluc. mediated pairing near magnetic QCP.
2. PG behavior in HF and PuMGa5 can be understood with the mag correlation.
3. Tc and T* are controlled by the mag. energy scales.
Can we jump into the HTSC ?
T
PG
NFL
FLAF
SC
T
HF SC (AFM)
x
SC
AF
NFL
FL
QCP
Magnetic Origin
HTSC Cuprates
QCP
Origin ?QCP
Some difference in phase diagrams for HF and HTSC.