Competing Interlayer Loop Currents and Superconductivity in the Bilayer t-J⊥-V Model
Abstract
The recent discovery of high-Tc superconductivity in pressurized and thin-film bilayer nickelates, featuring a strong interlayer exchange coupling, and their potential similarities with cuprate superconductors, has made this a very active topic in condensed matter physics. In the present paper we study the strongly correlated one-orbital (dx2−y2) bilayer t-J⊥-V model for nickelates, where V denotes the Coulomb interactions, using a controlled large-N expansion at and beyond the mean-field level. Focusing on the out-of-plane spin exchange interaction (J⊥), we find that it triggers both out-of-plane s-wave superconductivity and an out-of-plane bond-order phase (z-BOP) instability. The z-BOP gives rise to a complex z-axis hopping dominated by its imaginary component, which drives out-of-plane currents and induces in-plane ones, spontaneously forming on the vertical plaquettes a loop-current state that breaks time-reversal symmetry. Competition between this loop-current phase and superconductivity yields a dome-shaped superconducting region, with optimal superconductivity occurring near the z-BOP quantum critical point. The resulting phase diagram features a pure loop-current region, a low-doping coexistence phase, a pure superconducting state at higher doping, and a correlated metallic state.
Related
- Exact magnetic ground states and competing interlayer exchanges in layered kagome magnets
- Selective suppression of electronic orders via interlayer coupling in superconducting bilayer nickelate thin films
- Spectroscopic evidence of competing diagonal spin interactions and spin disproportionation in the bilayer nickelate La 3 Ni 2 O 7
- Interlayer pairing mechanism for bilayer nickelate superconductors
- Observation of superconductivity-induced leading-edge gap in a bilayer nickelate
BibTeX
@misc{zinni2026competing,
title = {{Competing Interlayer Loop Currents and Superconductivity in the Bilayer $t$-$J_\perp$-$V$ Model}},
author = {Luciano Zinni and Fabricio Gómez and Jun Zhan and Mat\'ıas Bejas and Xianxin Wu and Andreas P. Schnyder and Andrés Greco},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10926},
eprint = {2609.10926},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10926},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Competing Interlayer Loop Currents and Superconductivity in the Bilayer t-J_⊥-V Model
AU - Luciano Zinni
AU - Fabricio Gómez
AU - Jun Zhan
AU - Mat\'ıas Bejas
AU - Xianxin Wu
AU - Andreas P. Schnyder
AU - Andrés Greco
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.10926
UR - https://arxiv.org/abs/2609.10926
AB - The recent discovery of high-T_c superconductivity in pressurized and thin-film bilayer nickelates, featuring a strong interlayer exchange coupling, and their potential similarities with cuprate superconductors, has made this a very active topic in condensed matter physics. In the present paper we study the strongly correlated one-orbital (d_x^2−y^2) bilayer t-J_⊥-V model for nickelates, where V denotes the Coulomb interactions, using a controlled large-N expansion at and beyond the mean-field level. Focusing on the out-of-plane spin exchange interaction (J_⊥), we find that it triggers both out-of-plane s-wave superconductivity and an out-of-plane bond-order phase (z-BOP) instability. The z-BOP gives rise to a complex z-axis hopping dominated by its imaginary component, which drives out-of-plane currents and induces in-plane ones, spontaneously forming on the vertical plaquettes a loop-current state that breaks time-reversal symmetry. Competition between this loop-current phase and superconductivity yields a dome-shaped superconducting region, with optimal superconductivity occurring near the z-BOP quantum critical point. The resulting phase diagram features a pure loop-current region, a low-doping coexistence phase, a pure superconducting state at higher doping, and a correlated metallic state.
ER -