| Summary: | We study possible charge instabilities in doped Mott insulators by employing the two-dimensional t - J model with a positive value of the next nearest-neighbor hopping integral $t^{\prime} $ on a square lattice, which is applicable to electron-doped cuprates. Although the d -wave charge density wave (flux phase) and d -wave Pomeranchuk instability (nematic order) are dominant instabilities for a negative $t^{\prime} $ that corresponds to hole-doped cuprates, we find that those instabilities are strongly suppressed and become relevant only rather close to half filling. Instead, various types of bond orders with modulation vectors close to $(\pi ,\pi )$ are dominant in a moderate doping region. Phase separation is also enhanced, but it can be suppressed substantially by the nearest-neighbor Coulomb repulsion without affecting the aforementioned charge instabilities.
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