Magnetic phase diagram of a two-orbital model for bilayer nickelates varying doping
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| Autores principales: | , , , , , , |
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| Formato: | Preprint |
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2024
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| author | Lin, Ling-Fang Zhang, Yang Kaushal, Nitin Alvarez, Gonzalo Maier, Thomas A. Moreo, Adriana Dagotto, Elbio |
| author_facet | Lin, Ling-Fang Zhang, Yang Kaushal, Nitin Alvarez, Gonzalo Maier, Thomas A. Moreo, Adriana Dagotto, Elbio |
| contents | Motivated by the recently discovered high-$T_c$ bilayer nickelate superconductor La$_3$Ni$_2$O$_7$, we comprehensively research a bilayer $2\times2\times2$ cluster for different electronic densities $n$ by using the Lanczos method. We also employ the random-phase approximation to quantify the first magnetic instability with increasing Hubbard coupling strength, also varying $n$. Based on the spin structure factor $S(q)$, we have obtained a rich magnetic phase diagram in the plane defined by $n$ and $U/W$, at fixed Hund coupling. We have observed numerous states, such as A-AFM, Stripes, G-AFM, and C-AFM. For half-filling $n=2$ (two electrons per Ni site, corresponding to $N$ = 16 electrons), the canonical superexchange interaction leads to a robust G-AFM state $(π,π,π)$ with antiferromagnetic couplings in plane and between layers. By increasing or decreasing electronic densities, ferromagnetic tendencies emerge from the ``half-empty'' and ``half-full'' mechanisms, leading to many other interesting magnetic tendencies. In addition, the spin-spin correlations become weaker both in the hole or electron doping regions compared with half-filling. At $n = 1.5$ (or $N=12$), density corresponding to La$_3$Ni$_2$O$_7$, we obtained the ``Stripe 2'' ground state (antiferromagnetic coupling in one in-plane direction, ferromagnetic coupling in the other, and antiferromagnetic coupling along the $z$-axis) in the $2\times2\times2$ cluster. In addition, we obtained a much stronger AFM coupling along the $z$-axis than the magnetic coupling in the $xy$ plane. The random-phase approximation calculations with varying $n$ give very similar results as Lanczos. Meanwhile, a state with $q/π= (0.6, 0.6, 1)$ close to the E-phase wavevector is found in our RPA calculations by slightly reducing the filling to $n=1.25$, possibly responsible for the E-phase SDW recently observed in experiments. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2408_05689 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Magnetic phase diagram of a two-orbital model for bilayer nickelates varying doping Lin, Ling-Fang Zhang, Yang Kaushal, Nitin Alvarez, Gonzalo Maier, Thomas A. Moreo, Adriana Dagotto, Elbio Strongly Correlated Electrons Motivated by the recently discovered high-$T_c$ bilayer nickelate superconductor La$_3$Ni$_2$O$_7$, we comprehensively research a bilayer $2\times2\times2$ cluster for different electronic densities $n$ by using the Lanczos method. We also employ the random-phase approximation to quantify the first magnetic instability with increasing Hubbard coupling strength, also varying $n$. Based on the spin structure factor $S(q)$, we have obtained a rich magnetic phase diagram in the plane defined by $n$ and $U/W$, at fixed Hund coupling. We have observed numerous states, such as A-AFM, Stripes, G-AFM, and C-AFM. For half-filling $n=2$ (two electrons per Ni site, corresponding to $N$ = 16 electrons), the canonical superexchange interaction leads to a robust G-AFM state $(π,π,π)$ with antiferromagnetic couplings in plane and between layers. By increasing or decreasing electronic densities, ferromagnetic tendencies emerge from the ``half-empty'' and ``half-full'' mechanisms, leading to many other interesting magnetic tendencies. In addition, the spin-spin correlations become weaker both in the hole or electron doping regions compared with half-filling. At $n = 1.5$ (or $N=12$), density corresponding to La$_3$Ni$_2$O$_7$, we obtained the ``Stripe 2'' ground state (antiferromagnetic coupling in one in-plane direction, ferromagnetic coupling in the other, and antiferromagnetic coupling along the $z$-axis) in the $2\times2\times2$ cluster. In addition, we obtained a much stronger AFM coupling along the $z$-axis than the magnetic coupling in the $xy$ plane. The random-phase approximation calculations with varying $n$ give very similar results as Lanczos. Meanwhile, a state with $q/π= (0.6, 0.6, 1)$ close to the E-phase wavevector is found in our RPA calculations by slightly reducing the filling to $n=1.25$, possibly responsible for the E-phase SDW recently observed in experiments. |
| title | Magnetic phase diagram of a two-orbital model for bilayer nickelates varying doping |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2408.05689 |