Frustrated S = 1/2 Two-Leg Ladder with Different Leg Interactions

8th International Conference on Highly Frustrated Magnetism 2016

Tonegawa, Takashi^1,2 ; Okamoto, Kiyomi^3 ; Hikihara, Toshiya^4 ; Sakai, Tôru^5,6

Department Emeritus, Kobe University, Kobe

657-8501, Japan^1

Department of Physical Science, Osaka Prefecture University, Sakai

599-8531, Japan^2

College of Engineering, Shibaura Institute of Technology, Saitama

337-8570, Japan^3

Faculty of Science and Technology, Gunma University, Kiryu

376-8515, Japan^4

Graduate School of Material Science, University of Hyogo, Hyogo

678-1297, Japan^5

National Institutes for Quantum and Radiological Science and Technology (QST), SPring-8, Hyogo, 679-5148, Japan^6

关键词: Anisotropy parameters;    Density matrix renormalization group methods;    Direct product;    Exact diagonalization method;    Ground state phase diagram;    Haldane;    Nearest neighbors;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/828/1/012003/pdf
DOI  :  10.1088/1742-6596/828/1/012003

来源: IOP

【 摘 要 】

We explore the ground-state phase diagram of the S = 1/2 two-leg ladder. The isotropic leg interactions J1,aand J1,bbetween nearest neighbor spins in the legs a and b, respectively, are different from each other. The xy and z components of the uniform rung interactions are denoted by Jrand ΔJr, respectively, where Δ is the XXZ anisotropy parameter. This system has a frustration when J1,aJ1,br. The phase diagrams on the Δ (0≤Δ1,bplane in the cases of J1,a= - 0.2 and J1,a= 0.2 with Jr= -1 are determined numerically. We employ the physical consideration, the level spectroscopy analysis of the results obtained by the exact diagonalization method and also the density-matrix renormalization-group method. It is found that the non-collinear ferrimagnetic (NCFR) state appears as the ground state in the frustrated region of the parameters. Furthermore, the direct-product triplet-dimer (TD) state in which all rungs form the TD pair is the exact ground state, when J1,a+ J1,b= 0 and 0≤ Δ0.83. The obtained phase diagrams consist of the TD, XY and Haldane phases as well as the NCFR phase.