Seminars & Lectures
| * TITLE | [APCTP JRG Senimar] Orbital Fluctuation Mediated Superconductivity in Iron Pnictides based on the Five Orbital Hubbard-Holstein Model | ||||||
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| * DATE / TIME | 2010-04-07, 2:00pm | ||||||
| * PLACE | 512 Seminar room, APCTP Headquarters, POSTECH, Pohang, Korea | ||||||
| * ABSTRACT | |||||||
| The mechanism of superconductivity in iron pnictides has been an important open problem. Although spin fluctuation theories predict the sign-reversing s-wave state (s+--wave state), there are several serious discrepancies for the s+--wave state. For example, although s+--wave state is expected to be very fragile against impurities due to the interband scattering [1], the superconducting (SC) state is remarkably robust against impurities. Moreover, ``resonance-like\'\' peak structure observed by neutron scattering measurements is reproduced by considering the strong correlation effect via quasiparticle damping, without the necessity of sign reversal in the SC gap [2]. Here, we show that the moderate electron-phonon interaction due to the Fe-ion oscillation can induce the critical d-orbital fluctuations, without being prohibited by the Coulomb interaction [3]. These fluctuations give rise to the strong pairing interaction for the s-wave superconducting (SC) state without sign reversal (s++-wave state). When spin fluctuations are also strong, the SC state shows a smooth crossover from s+--wave state to s++-wave state as impurity concentration increases. [1] S. Onari and H. Kontani, Phys. Rev. Lett. 103, 177001 (2009). [2] S. Onari, H. Kontani, and M. Sato, Phys. Rev. B 81, 060504(R) (2010). [3]H. Kontani and S. Onari, arXiv:0912.1975. |
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