Nature of stripes in the generalized t?J model applied to the cuprate superconductors
A recent study of the transport properties on the stripe phase in La1.875Ba01.25CuO4 by Li et al (2007 Phys. Rev. Lett. 99 067001) found two-dimensional (2D) superconductivity over a wide temperature range including a Berezinski–Kosterlitz–Thouless transition at a temperature T=16 K, with 3D superconducting (SC) ordering only at T=4 K. These results contradict the long standing belief that the onset of superconductivity is suppressed by stripe ordering and suggest coexistence of stripe and SC phases. The lack of 3D SC order above T=4 K requires an antiphase ordering in the SC state to suppress the interlayer Josephson coupling as proposed by Berg et al (2007 Phys. Rev. Lett. 99 127003). Here, we use a renormalized mean field theory for a generalized t–J model to examine in detail the energetics of the spin and charge stripe ordered SC states including possible antiphase domains in the SC order. We find that the energies of these modulated states are very close to each other and that the anisotropy present in the low temperature tetragonal crystal structure favors stripe resonating valence bond states. The stripe antiphase SC states are found to have energies very close to, but always above, the ground state energy, which suggests additional physical effects are responsible for their stability.