Exact dimer ground state and quantum phase transitions in a coupled spin ladder
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| Format: | Preprint |
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2026
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| _version_ | 1866915798070591488 |
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| author | Mahapatra, Manas Ranjan Kumar, Rakesh |
| author_facet | Mahapatra, Manas Ranjan Kumar, Rakesh |
| contents | Spin ladders are key models that act as intermediaries between one-dimensional and two-dimensional spin systems. In this study, we examine a coupled spin-$1/2$ ladder, where frustrated ladders with leg, rung, and diagonal interactions are linked through a horizontal coupling. By introducing a spatially anisotropic third-nearest-neighbor interaction along the horizontal direction, the model was found to possess an exact dimer ground state, characterized by a product of singlets forming a columnar dimer phase. The model is analyzed using bond-operator mean-field theory (BOMFT) and the density matrix renormalization group (DMRG). BOMFT reveals three distinct phases: a double-stripe ordered phase, a Néel ordered phase, and a quantum disordered dimerized phase. The critical points for the transitions are $J_1 = -0.81$ (double-stripe to dimerized) and $J_1 = 2.81$ (dimerized to Néel phase). DMRG results corroborate the exact ground state and refine the critical points to $J_1 = -0.79$ and $J_1 = 2.29$ for the respective transitions. Additionally, another transition is identified as the Néel order vanishes for $J_1 > 4.5$. The static spin structure factor further corroborates the nature of the ordered phases. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2602_13406 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Exact dimer ground state and quantum phase transitions in a coupled spin ladder Mahapatra, Manas Ranjan Kumar, Rakesh Strongly Correlated Electrons Spin ladders are key models that act as intermediaries between one-dimensional and two-dimensional spin systems. In this study, we examine a coupled spin-$1/2$ ladder, where frustrated ladders with leg, rung, and diagonal interactions are linked through a horizontal coupling. By introducing a spatially anisotropic third-nearest-neighbor interaction along the horizontal direction, the model was found to possess an exact dimer ground state, characterized by a product of singlets forming a columnar dimer phase. The model is analyzed using bond-operator mean-field theory (BOMFT) and the density matrix renormalization group (DMRG). BOMFT reveals three distinct phases: a double-stripe ordered phase, a Néel ordered phase, and a quantum disordered dimerized phase. The critical points for the transitions are $J_1 = -0.81$ (double-stripe to dimerized) and $J_1 = 2.81$ (dimerized to Néel phase). DMRG results corroborate the exact ground state and refine the critical points to $J_1 = -0.79$ and $J_1 = 2.29$ for the respective transitions. Additionally, another transition is identified as the Néel order vanishes for $J_1 > 4.5$. The static spin structure factor further corroborates the nature of the ordered phases. |
| title | Exact dimer ground state and quantum phase transitions in a coupled spin ladder |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2602.13406 |