Interplay between superconductivity and flux phase in the t−J model

E. Cappelluti; R. Zeyher

doi:10.1103/PhysRevB.59.6475

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Interplay between superconductivity and flux phase in the t−J model

E. Cappelluti, R. Zeyher

DOI 10.1103/PhysRevB.59.6475 · Physical Review B

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Abstract

We study the phase diagram of the t−J model using a mean field type approximation within the Baym-Kadanoff perturbation expansion for Hubbard X operators. The line separating the normal state from a d-wave flux or bond-order state starts near optimal doping at T=0 and rises quickly with decreasing doping. The transition temperature Tc for d-wave superconductivity increases monotonically in the overdoped region towards optimal doping. Near optimal doping a strong competition between the two d-wave order parameters sets in leading to a strong suppression of Tc in the underdoped region. Treating for simplicity the flux phase as commensurate the superconducting and flux phases coexist in the underdoped region below Tc, whereas a pure flux phase exists above Tc with a pseudogap of d-wave symmetry in the excitation spectrum. We also find that incommensurate charge-density-wave ground states due to Coulomb interactions do not modify strongly the above phase diagram near the superconducting phase, at least, as long as the latter exists at all.