Magnetism and superconductivity in the t-J model

Various ordered states are examined in the weak-coupling regime of the t-J model on the basis of a Mott-Hubbard and Gutzwiller picture, or by assuming the formation of heavy electrons at the top of the lower Hubbard band, as shown by an auxiliary-particle theory [F. J. Ohkawa, J. Phys. Soc. Jpn. 58, 4156 (1989)]. Spin-density-wave (SDW) states and anisotropic superconducting (SC) states can compete with each other. However, other ordered states, such as charge-density-wave states, bond-order states, flux phases, and broken-chiral-symmetry states, are less favorable than SDW states and anisotropic SC states. The results are discussed in connection with recently discovered high-critical-temperature superconductors