Out-of-plane bond-order phase, superconductivity, and their competition in the t- J∥−J⊥ model: Possible implications for bilayer nickelates

Abstract

Almost four decades of intense research have been invested to study the physics of high-Tc cuprate superconductors. The recent discovery of high-Tc superconductivity in pressurized bilayer nickelates and its potential similarities with cuprate superconductors may open a new window to understand this long-standing problem. We have studied the proposed bilayer t−J∥−J⊥ model [where J∥ (J⊥) is the in-plane (out-of-plane) magnetic exchange] in a large-N approach on the basis of the path integral representation for Hubbard operators, which allows to obtain results at mean-field and beyond mean-field level. We find that J⊥ is a candidate for triggering high superconducting Tc values at quarter filling (hole doping δ=0.5) of the dx2−y2 orbitals. Beyond mean-field level, we find a new phase, an out-of-plane bond-order phase (z-BOP), triggered also by J⊥. z-BOP develops below a critical temperature which decreases with increasing doping and vanishes at a quantum critical point below quarter filling. The occurrence of this phase and its competition with superconductivity leads to a superconducting dome-shaped behavior as a function of doping and as a function of J⊥. Qualitative comparisons with the physics of cuprates and the recent literature on the new pressurized nickelates are given along the paper.

Source-reported materials — not catalogue approval

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