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| 題目 |
Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors |
| 講師 |
Prof. Ilya Eremin
Max-Planck-Institut fur Physik komplexer Systeme, Germany
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| 日時 |
平成20年10月6日 16：00～17：30 |
| 場所 |
コラボレーション棟4F 共同研究室 |
| 要旨 |
Recent discovery of superconductivity in the iron-based layered pnictides of both oxygen containing RFeAsO (R=La, Nd, Sm) and oxygen free AFe2As2 (A=Ba, Sr, Ca)
with Tc ranging between 26 and 52K generated enormous interest in the physics of these materials.
Like the cuprates, the pnictides are highly two-dimensional, their parent material shows antiferromagnetic long-range order below 150K,
and superconductivity occurs upon doping of either electrons or holes into the FeAs layers.
We analyze antiferromagnetism and superconductivity in novel Fe-based superconductors within the itinerant model of small electron and hole pockets near (0; 0) and (?,?).
We argue that the effective interactions in both channels logarithmically flow towards the same values at low energies, i.e.,
antiferromagnetism and superconductivity must be treated on equal footings. The magnetic instability comes first for equal sizes of the two pockets,
but looses to superconductivity upon doping. The superconducting gap has no nodes, but changes sign between the two Fermi surfaces (extended s-wave symmetry).
We argue that the T dependencies of the spin susceptibility and NMR relaxation rate for such state are exponential only at very low T,
and can be well fitted by power-laws over a wide T range below Tc.
[1] M. Korshunov, and I. Eremin, arXiv:0804.1793 (unpublished)
[2] A.V. Chubukov, D. Efremov, I. Eremin, arXiv:0807.3735 (unpublished) [3] M.M. Korshunov and I. Eremin, Europhys. Lett. 83, xxxx (2008) in press
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| 世話人 |
理学部物理学科 鄭 国慶 （内線：7813） |
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