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.