Holes in thet−Jzmodel: A diagrammatic study

Abstract

The t-J z model is the strongly anisotropic limit of the t-J model which captures some general properties of doped antiferromagnets ͑AF's͒. The absence of spin fluctuations simplifies the analytical treatment of hole motion in an AF background, and allows us to calculate single-and two-hole spectra with a high accuracy using a regular diagram technique combined with a real-space approach. At the same time, numerical studies of this model via exact diagonalization on small clusters show negligible finite-size effects for a number of quantities, thus allowing a direct comparison between analytical and numerical results. Both approaches demonstrate that the holes have a tendency to pair in p-and d-wave channels at realistic values of t/J. Interactions leading to pairing and effects selecting p and d waves are thoroughly investigated. The role of transverse spin fluctuations is considered using perturbation theory. Based on the results of the present study, we discuss the pairing problem in the realistic t-J-like model. Possible implications for preformed pairs formation and phase separation are drawn. ͓S0163-1829͑99͒04127-2͔

Low-energy states with different symmetries in thet−Jmodel with two holes on a 32-site lattice

“…Note that this trend is consistent with the prediction from the spin polaron picture. 9,10,18 While at JϾ0.3t the p (,) and p (,0) states are clearly excited states, the energy levels look quite complicated in the range 0.2tрJр0.3t. Note that the d, p (,) and p (,0) states are almost degenerate at Jϭ0.3t, although the d state is still the ground state.…”

“…Furthermore, it has been shown that such terms favor the p-wave state. 10 This shows that the physics of the low-lying p state may not be irrelevant. Therefore it is important to understand the similarities and differences between the properties of the d x 2 Ϫy 2 and the p states.…”

“…Recently the question of the robustness of d-wave pairing was addressed by using the anisotropic t-J z model as the starting point. 10 It concluded that different mechanisms may select states with different symmetries and their competition may destroy the d-wave ground state. This raises doubt on the robustness of the d-wave ground state because it is known that the t-J model alone is not enough to explain fully the hole dynamics of Sr 2 CuO 2 Cl 2 measured by angle-resolved photoemission.…”

Hole-pair symmetry and excitations in the strong-coupling extendedt−Jzmodel: competition betweend-wave andFye1, Martins2, Dagotto3 2004Phys. Rev. B3010View full textAdd to dashboardCite

“…= 0, the t ′ − J z − J ⊥ model hole pair symmetry on a plaquette is d-wave for t ′ > 0 and s-wave for t ′ < 0, as in the general t ′ − J z model strong coupling case. As mentioned previously, some approaches have suggested p-wave hole-pair symmetry for some range of generally intermediate or small J/t or J z /t 20,31,32,33 . However, other t − J numerical results 22,34,35,37 indicate that d-wave features of the strong-coupling limit may persist down to physically relevant intermediate coupling (J/t ≈ 0.3 − 0.5).…”

Edge States in Doped Antiferromagnetic Nanostructures

“…4,5 One can argue that the t-J z model should reproduce qualitatively the holes' ground state of the isotropic t-J model, although the details of such states might differ. Moreover, for the bulk stripe phase in this model a very close quantitative agreement between the analytical and numerical methods have been demonstrated in our previous work.…”