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Theoretical Study on the Multiple-exchange Interactions in Two-dimensional Quantum Solids

二维量子固体多重交换相互作用的理论研究

基本信息

批准号：
10203202
负责人：
KUBO Kenn
金额：
$ 2.88万
依托单位：
Aoyama Gakuin University (1999-2001)University of Tsukuba (1998)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10203202/
关键词：
^3He solid layers multiple-spin exchange triangular lattice spin model chiral phase transition magnetization plateau frustration Monte Carlo method ヘリウム3固体薄膜 3角格子非整合整合相転移スピン波カイラリティー相転移多体交換相互作用 ^3He薄膜固体三角格子

项目摘要

(a) We investigated the groundstate of the spin system on the triangular lattice with 2-(strength J) and 4-spin(strngth K) exchange interactions and obtained following results : (a)The tetrahedral ground state with scalr chirality is realized when the 4-spin exchange is dominant. We investigated the finite temperature phase transition by Monte Carlo simulations and found that the transition is of the first order. (b) We established by means of the mean field theory and the diagnalization of finite clusters that the magnetization curve shows a 1/2-plateau behavior when J/K = -6〜2. We showed that the plateau is realized by uuud state with translational symmetry breaking and and leads to a sharp phase transition at a finite temperature. (c) The 120°Neel state is destabilized by 4-spin exchange interactions at J/K = 10. A novel groundstate with 6 sublattices is stable in a region where J/K < lO. Furthermore we found various novel groundstates with large spatial structures for -8.6 < J/K < -2. We also investigated the effect of the external magnetic field and found that the magnetic field stabilizes several new ground states.(b) We investiated the incommensurate-commensurate transition in ^3He solid layers. The transition was interpreted as a phase transition of a two-dimensional soliton lattice.(c) We improved the multicanonical Monte Carlo method and applied it to the 3-dimensional ±J Ising model. Our eresult supports the droplet picture of the spin glass phase.

(a)研究了具有2-（强度J）和4-（强度K）交换相互作用的三角晶格上自旋体系的基态，得到以下结果：(a)当4-自旋交换占主导地位时，实现了具有标度手性的四面体基态。通过蒙特卡罗模拟研究了有限温度相变，发现相变是一阶的。(b)利用平均场理论和有限团簇的对角化，证明当J/K = -6 ~ 2时，磁化曲线呈现1/2平台特性。我们证明了平台是由具有平移对称性破缺的uud态实现的，并导致了在有限温度下的急剧相变。(c)在J/K = 10时，4自旋交换作用使120°Neel态失稳。具有6个子晶格的新型基态在J/K < lO的区域是稳定的。此外，我们还发现了-8.6 < J/K < -2时具有大空间结构的新基态。我们还研究了外磁场的作用，发现磁场稳定了几个新的基态。(b)我们研究了^3He固体层的不相称转变。这种转变被解释为二维孤子晶格的相变。(c)改进了多声次蒙特卡罗方法，并将其应用于三维±jising模型。我们的结果支持自旋玻璃相的液滴图像。