Friday, June 7, 2013

1306.1434 (Takahiro Misawa et al.)

Origin of High-Tc Superconductivity in the Doped Hubbard Model and Its

Takahiro Misawa, Masatoshi Imada
Superconductors whose critical temperatures (Tc) are higher than 40K are called high-Tc superconductors. Such high Tc has been speculated to be unaccountable by the standard Bardeen-Cooper-Schrieffer (BCS) theory, in which the electron-phonon interactions play an essential role. Instead, strong electronic correlations are considered to be a key to understand nature of the high-Tc superconductors, for which the doped Hubbard model is one of the simplest models. However, despite numerous studies of the Hubbard model, origins of the high-Tc superconductivity are still under hot debates. Here, by performing state-of-the-art calculations of extended doped Hubbard models, we first elucidate that the superconductivity in the Hubbard model is mostly preempted by the phase separation and vulnerable to realistic intersite interactions. By introducing intersite interactions, we quantitatively identify an origin of high-Tc superconductivity, as the instability toward the phase separation caused by the local charge fluctuations, synergetically supplemented by local antiferromagnetic (singlet) fluctuations.
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