Spin Fluctuation, Orbital States and Non-conventional Superconductivity in Actinides Compounds

2012 ◽  
Vol 1444 ◽  
Author(s):  
S. Kambe ◽  
H. Sakai ◽  
Y. Tokunaga
Keyword(s):  
Spin Fluctuation ◽  
Pairing Symmetry ◽  
Unconventional Superconductivity ◽  
Superconducting Transition ◽  
Magnetic Fluctuations ◽  
Fermi Surfaces ◽  
Unconventional Superconductors ◽  
Wave Pairing ◽  
Superconducting Pairing ◽  
Orbital Character

ABSTRACTIn d-wave unconventional superconductors, superconducting Cooper pairs are believed to be formed via magnetic fluctuations. In fact, the superconducting transition temperature Tc roughly correlates with the antiferromagnetic spin fluctuation energy in d-wave unconventional superconductors including high Tc cuprates. In addition to this correlation, the superconducting pairing symmetry and the magnetic anisotropy of the normal state are found empirically to be strongly correlated in f-electron unconventional superconductors having crystallographic symmetry lower than cubic. In antiferromagnetic systems, unconventional superconductivity appears with singlet (d-wave) pairing for cases of XY anisotropy. In contrast, in ferromagnetic systems, unconventional superconductivity with triplet (e.g. p-wave) pairing appears for cases of Ising anisotropy. In this report, the d-wave case is addressed, the origin of XY anisotropy is discussed in terms of the orbital character; and the angular momentum character jz for each piece of Fermi surfaces is determined.

Spin fluctuations, Fermi surface hotspots and nesting in PuCoGa5

2014 ◽  
Vol 1683 ◽  
Author(s):  
Matthias J. Graf ◽  
Tanmoy Das ◽  
Jian-Xin Zhu
Keyword(s):  
Spin Fluctuation ◽  
Pairing Symmetry ◽  
Spin Fluctuations ◽  
Gap Functions ◽  
Fermi Surfaces ◽  
Unconventional Superconductors ◽  
Magnetic Spin ◽  
The Many ◽  
Superconducting Pairing ◽  
Strong Spin

ABSTRACTSurprisingly little is known about the mechanism and symmetry of superconducting pairing in PuCoGa5. A common thread with other unconventional superconductors is the presence of spin fluctuations in the normal state, which in this particular case is controlled by strong spin–orbit coupling split bands. The many and anisotropic Fermi surfaces make the guessing of the potential spin-fluctuation nesting vector and resulting symmetry of the pairing function a nontrivial task. To provide much needed guidance for the identification of the pairing symmetry in this multiband superconductor, we perform first-principles based magnetic spin susceptibility calculations to identify the dominant nesting vectors that potentially give rise to interband pairing with nodal d- or s±-wave gap functions.

INTENSITY OF NMR SIGNAL IN La1.90Sr0.10CuO4: CHARGE vs. SPIN FREEZING

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2791-2796
Author(s):  
M.-H. JULIEN ◽  
A. CAMPANA
Keyword(s):  
Spin Fluctuation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Simple Calculation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Superconducting Transition ◽  
Magnetic Fluctuations ◽  
Spin Lattice ◽  
Spin Freezing

We report on 139 La NMR and 63 Cu NQR measurements in La 1.90 Sr 0.10 CuO 4 above its superconducting transition temperature. We find that the intensity of the signal integrated on frequencies decreases significantly on cooling from 60 K to 28 K for 63 Cu nuclei (wipeout effect), while it remains constant for 139 La nuclei in this T-range. The distribution of 139 La spin-lattice relaxation time (T1) values in the "wipeout regime" reveals a spread of electronic fluctuation frequencies in CuO 2 planes. A simple calculation, for spin fluctuation induced relaxation, shows that 63 Cu nuclei at sites where electronic fluctuations are slowest should not be observable because of too short relaxation times. This means that the 63 Cu NQR wipeout effect may be explained primarily by slow magnetic fluctuations.

UNCONVENTIONAL SUPERCONDUCTIVITY IN UPt3: FREQUENCY DEPENDENT AC SUSCEPTIBILITY

1993 ◽  
Vol 07 (01n03) ◽  
pp. 18-21
Author(s):  
Z. KOZIOL ◽  
J. J. M. FRANSE ◽  
A. A. MENOVSKY
Keyword(s):  
Normal State ◽  
Surface Resistance ◽  
Skin Effect ◽  
Ac Susceptibility ◽  
Response Characteristic ◽  
Complex Conductivity ◽  
Unconventional Superconductivity ◽  
Superconducting Transition ◽  
Good Qualitative Agreement ◽  
Unconventional Superconductor

A method has been developed for measuring and analysing the complex ac susceptibility of a metal undergoing a superconducting transition, in case there exists an interplay between the normal-state skin-effect and the response characteristic for the superconducting state. For the unconventional superconductor UPt 3, the study of the temperature and frequency dependence of the complex conductivity close to T c has resulted in predictions for the surface resistance and the radio-frequency susceptibility which are in a good qualitative agreement with published experimental results.

Break junction measurements on Bi2Sr2Ca1Cu2O8+x single crystals: analysis of the superconducting pairing symmetry

1997 ◽  
Vol 280 (1-2) ◽  
pp. 71-76 ◽  
Author(s):  
H. Hancotte ◽  
D.N. Danydov ◽  
R. Deltour ◽  
A.G.M. Jansen ◽  
P. Wyder
Keyword(s):  
Single Crystals ◽  
Pairing Symmetry ◽  
Break Junction ◽  
Superconducting Pairing

OCCURRENCE OF SPIN-FLUCTUATION PAIRING IN HIGH-TEMPERATURE SUPERCONDUCTORS

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3635-3641 ◽  
Author(s):  
Howard A. Blackstead ◽  
John D. Dow
Keyword(s):  
High Temperature ◽  
Cooper Pair ◽  
Spin Fluctuation ◽  
High Temperature Superconductors ◽  
Wave Pairing ◽  
D Wave

The definitive property of a spin-fluctuation d-wave-pairing superconductor is that cuprate-plane Cu-site Ni is a weaker Cooper-pair-breaker than Zn on the same site. None of the major high-temperature superconductors, except possibly YBa 2 Cu 3 O x, exhibits this property experimentally.

SPATIAL FLUCTUATIONS OF THE ORDER PARAMETER IN A DISORDERED SUPERCONDUCTOR WITH p-WAVE PAIRING

2002 ◽  
Vol 16 (03) ◽  
pp. 453-461 ◽  
Author(s):  
GRZEGORZ LITAK
Keyword(s):  
Perturbation Method ◽  
Hubbard Model ◽  
Order Parameter ◽  
Pairing Symmetry ◽  
P Wave ◽  
Real Solution ◽  
The Real ◽  
Wave Pairing ◽  
Spatial Fluctuations ◽  
Effect Of Disorder

The effect of nonmagnetic disorder on the pairing amplitude is studied by means of a perturbation method. Using an extended one band Hubbard model with an intersite attraction we analyze various solutions of p-wave pairing symmetry and discuss their instability calculating fluctuations of order parameter. The model is applied to describe the effect of disorder in Sr2RuO4. The results shows that the real solution with line nodes can be favoured by disorder.

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