Unconventional superconductivity originating from disconnected Fermi surfaces in iron pnictides

The superconductivity and magnetic phenomena of the rare earth iron pnictides R FePO (R = La , Sm ) are analyzed using ab initio density functional theory in the local density approximation (LDA) with the on-site Hubbard U eff parameter (LDA + U). The results of the magnetic properties, band structures and Fermi surfaces of the recently synthesized tetragonal layered iron pnictides superconductor SmFePO are presented in comparison with the superconductor LaFePO . The anti-ferromagnetic state [ Sm : AFM, Fe AFM_stripe] is found to be the most stable than the other possible phases, which is in agreement with experiment. The effect of the Hubbard correction is investigated and is found to be a necessary requirement for the accurate description of both the electronic structure and the Fermi surfaces.

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Small-qphonon-mediated unconventional superconductivity in the iron pnictides

Physical Review B ◽

10.1103/physrevb.83.092505 ◽

2011 ◽

Vol 83 (9) ◽

Cited By ~ 17

Author(s):

A. Aperis ◽

P. Kotetes ◽

G. Varelogiannis ◽

P. M. Oppeneer

Keyword(s):

Iron Pnictides ◽

Unconventional Superconductivity

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

MRS Proceedings ◽

10.1557/opl.2012.945 ◽

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.

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