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arXiv · 0808.3742

Valley density-wave and multiband superconductivity in Fe-pnictides

Vladimir Cvetkovic·Zlatko Tesanovic
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Abstract

The key feature of the Fe-based superconductors is their quasi 2D multiband Fermi surface. By relating the problem to a negative U Hubbard model and its superconducting ground state, we show that the defining instability of such a Fermi surface is the valley density-wave (VDW), a combined spin/charge density-wave at the wavevector connecting the electron and hole valleys. As the valley parameters change by doping or pressure, the fictitious superconductor experiences "Zeeman splitting", eventually going into a non-uniform "Fulde-Ferrell-Larkin-Ovchinikov" (FFLO) state, an itinerant and often incommensurate VDW of the real world, characterized by the metallic conductivity from the ungapped remnants of the Fermi surface. When "Zeeman splitting" exceeds the "Chandrasekhar-Clogston" limit, the "FFLO" state disappears, and the VDW is destabilized. Near this point, the VDW fluctuations and interband pair repulsion are essential ingredients of high-Tc superconductivity in Fe-pnictides.

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Vladimir Cvetkovic, Zlatko Tesanovic. 2009-06-15. Valley density-wave and multiband superconductivity in Fe-pnictides. https://doi.org/10.1103/physrevb.80.024512

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