TY - JOUR
T1 - Kinetic-energy pairing and condensation energy in cuprates
AU - Ogata, Masao
AU - Yokoyama, Hisatoshi
AU - Yanase, Youichi
AU - Tanaka, Yukio
AU - Tsuchiura, Hiroki
PY - 2006/1/1
Y1 - 2006/1/1
N2 - In order to study the condensation energy in cuprates and the possibility of kinetic-energy pairing, we study the two-dimensional Hubbard model on a square lattice near half-filling using a variational Monte Carlo method for superconductivity. We modify the variational wave function by taking account of the nearest-neighbor correlation between holons and doublons. It is found that there is a qualitative difference between the weak-coupling region and the strong-coupling region. In the strong-coupling region (U≳Uco), the energy gain at the superconducting transition is derived from the kinetic-energy, while in the weak-coupling region (U≲Uco), a conventional BCS-type potential-energy gain occurs. Condensation energy is large in the strong-coupling side and expressed as ∝exp(-4at/J) with a being a constant and J=4t2/U. This result with recent experiments of optical conductivity implies that cuprate superconductors belong to the strong-coupling region. Similar but slightly different condensation energy is also obtained in the calculation using the fluctuation exchange (FLEX) approximation.
AB - In order to study the condensation energy in cuprates and the possibility of kinetic-energy pairing, we study the two-dimensional Hubbard model on a square lattice near half-filling using a variational Monte Carlo method for superconductivity. We modify the variational wave function by taking account of the nearest-neighbor correlation between holons and doublons. It is found that there is a qualitative difference between the weak-coupling region and the strong-coupling region. In the strong-coupling region (U≳Uco), the energy gain at the superconducting transition is derived from the kinetic-energy, while in the weak-coupling region (U≲Uco), a conventional BCS-type potential-energy gain occurs. Condensation energy is large in the strong-coupling side and expressed as ∝exp(-4at/J) with a being a constant and J=4t2/U. This result with recent experiments of optical conductivity implies that cuprate superconductors belong to the strong-coupling region. Similar but slightly different condensation energy is also obtained in the calculation using the fluctuation exchange (FLEX) approximation.
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U2 - 10.1016/j.jpcs.2005.10.017
DO - 10.1016/j.jpcs.2005.10.017
M3 - Article
AN - SCOPUS:33645058209
VL - 67
SP - 37
EP - 40
JO - Journal of Physics and Chemistry of Solids
JF - Journal of Physics and Chemistry of Solids
SN - 0022-3697
IS - 1-3
ER -