We investigate a generalized inhomogeneous two-dimensional Ising model on the kagomé lattice with two alternating couplings $J_i$ and $J'_i$ , $i=1,2,3$ , along the three lattice directions. The local Boltzmann weights are mapped onto a non-symmetric eight-vertex $R$ -matrix satisfying the free-fermion condition for arbitrary values of the six couplings. We analyze the Yang--Baxter structure for the cases $J'_i=J_i$ and $J'_i=-J_i$ and derive the corresponding one-dimensional quantum spin chains in the anisotropic limit. The first case yields a transverse-field Ising-type Hamiltonian, while the second leads to a modified chain with a graded permutation structure and shifted partition-function zeros. For a partially anisotropic model, we also obtain the free energy and specific heat.We investigate a generalized inhomogeneous two-dimensional Ising model on the kagomé lattice with two alternating couplings $J_i$ and $J'_i$, $i=1,2,3$, along the three lattice directions. The local Boltzmann weights are mapped onto a non-symmetric eight-vertex $R$-matrix satisfying the free-fermion condition for arbitrary values of the six couplings. We analyze the Yang--Baxter structure for the cases $J'_i=J_i$ and $J'_i=-J_i$ and derive the corresponding one-dimensional quantum spin chains in the anisotropic limit. The first case yields a transverse-field Ising-type Hamiltonian, while the second leads to a modified chain with a graded permutation structure and shifted partition-function zeros. For a partially anisotropic model, we also obtain the free energy and specific heat.

arXiv:2609.10163Sep 9, 20260 citations

Anisotropic ising model on 2D Kagomé lattice as an inhomogeneous XYZ integrable model

Shahane A. Khachatryan, Hrachia Babujian, A. Sedrakyan

We investigate a generalized inhomogeneous two-dimensional Ising model on the kagomé lattice with two alternating couplings J i and J i ′ , i = 1 , 2 , 3 , along the three lattice directions. The local Boltzmann weights are mapped onto a non-symmetric eight-vertex R -matrix satisfying the free-fermion condition for arbitrary values of the six couplings. We analyze the Yang–Baxter structure for the cases J i ′ = J i and J i ′ = − J i and derive the corresponding one-dimensional quantum spin chains in the anisotropic limit. The first case yields a transverse-field Ising-type Hamiltonian, while the second leads to a modified chain with a graded permutation structure and shifted partition-function zeros. For a partially anisotropic model, we also obtain the free energy and specific heat.We investigate a generalized inhomogeneous two-dimensional Ising model on the kagomé lattice with two alternating couplings J i and J i ′ , i = 1 , 2 , 3 , along the three lattice directions. The local Boltzmann weights are mapped onto a non-symmetric eight-vertex R -matrix satisfying the free-fermion condition for arbitrary values of the six couplings. We analyze the Yang–Baxter structure for the cases J i ′ = J i and J i ′ = − J i and derive the corresponding one-dimensional quantum spin chains in the anisotropic limit. The first case yields a transverse-field Ising-type Hamiltonian, while the second leads to a modified chain with a graded permutation structure and shifted partition-function zeros. For a partially anisotropic model, we also obtain the free energy and specific heat.

Nuclear Physics BOct 5, 20260 citations

Fermionization of a Generalized Two-Dimensional Ising Model

A. I. Bugrij

Research reports in physicsJan 1, 19914 citations

Free-Fermion Models and Two-Dimensional Ising Models Under Zero Field and Imaginary Field i(π/2)kBT

De-Zhang Li, Xin Wang, Xiao‐Bao Yang

The Ising model is famous in condensed matter and statistical physics. In this work we present a free-fermion formulation of the two-dimensional classical Ising models on honeycomb, triangular and Kagomé lattices. Each Ising model is studied in the cases of a zero field and of an imaginary field i(π/2)kBT. We employ the decorated lattice technique, star-triangle transformation, and weak-graph expansion method to exactly map each Ising model in both cases into an eight-vertex model on the square lattice. The resulting vertex weights are shown to satisfy the free-fermion condition. In the zero-field case, each Ising model is an even free-fermion model. In the case of the imaginary field, the Ising model on the honeycomb lattice is an even free-fermion model, while the models on the triangular and Kagomé lattices are odd free-fermion models. We obtain the exact solution of the Kagomé lattice Ising model under the imaginary field i(π/2)kBT, a result not previously reported in the literature. We also show that the frustrated Ising models on the triangular and Kagomé lattices in the imaginary field still exhibit a non-zero residual entropy.The Ising model is famous in condensed matter and statistical physics. In this work we present a free-fermion formulation of the two-dimensional classical Ising models on honeycomb, triangular and Kagomé lattices. Each Ising model is studied in the cases of a zero field and of an imaginary field i(π/2)kBT. We employ the decorated lattice technique, star-triangle transformation, and weak-graph expansion method to exactly map each Ising model in both cases into an eight-vertex model on the square lattice. The resulting vertex weights are shown to satisfy the free-fermion condition. In the zero-field case, each Ising model is an even free-fermion model. In the case of the imaginary field, the Ising model on the honeycomb lattice is an even free-fermion model, while the models on the triangular and Kagomé lattices are odd free-fermion models. We obtain the exact solution of the Kagomé lattice Ising model under the imaginary field i(π/2)kBT, a result not previously reported in the literature. We also show that the frustrated Ising models on the triangular and Kagomé lattices in the imaginary field still exhibit a non-zero residual entropy.

arXiv:2406.00232EntropyJul 27, 20253 citations

Susceptibility of the Kagom� lattice Ising model

M. D�bauche, Héctor Giacomini

Journal of Statistical PhysicsMar 1, 19900 citations

We investigate a generalized inhomogeneous two-dimensional Ising model on the kagomé lattice with two alternating couplings

J_i

and

J'_i

i=1,2,3

, along the three lattice directions. The local Boltzmann weights are mapped onto a non-symmetric eight-vertex

R

-matrix satisfying the free-fermion condition for arbitrary values of the six couplings. We analyze the Yang--Baxter structure for the cases

J'_i=J_i

and

J'_i=-J_i

and derive the corresponding one-dimensional quantum spin chains in the anisotropic limit. The first case yields a transverse-field Ising-type Hamiltonian, while the second leads to a modified chain with a graded permutation structure and shifted partition-function zeros. For a partially anisotropic model, we also obtain the free energy and specific heat.