Unifying Approaches to Novel Quantum Phases in Low-Dimensional Magnets

低维磁体中新型量子相的统一方法

• 批准号: 18540372
• 负责人: TOTSUKA Keisuke
• 金额: $ 1.31万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2006
• 资助国家: 日本
• 起止时间: 2006 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18540372/
• 关键词: Low-dimensional quantum spin systems; Multi-spin exchange interactions; Chiral orders; spin-nematic orders; Bse-Einstein condensation of spins; フラストレーション系; 量子スピン系; 多体交換相互作用; マグノンBEC; スピンネマティック秩序; 競合秩序; 量子相転移; sine-Gordon模型; contractor renorma

Construction of unifying theories for competing orders in one- and two dimensional quantum magnets which contain multi-spin exchange interactions. The effect of multi-spin exchange interactions (ring-exchange interaction, in particular) is intriguing in its own right since these interactions are thought of as diving hoes of many exotic quantum phases. We determined the global phase structures of ladder-type models which exhibit new kinds of phases (e.g. staggered dimer, staggered scalar chiral, nematic, etc.) from a unifying viewpoint based on high symmetries. Our analysis shows that the basic phase structure of these systems can be understood by considering effective Bose liquids with spins (S=1). We also extended our methods to two-dimensional cases by using the contractor-renormalization (CORE) method.A first step toward the understanding of the ground-state phases of spin-1 triangular lattice antiferromagnets. The discovery of a new spin-1 two-dimensional antiferromagnet on a triangular lattice sparked interests on various ground-state phases in S=1 triangular-lattice antiferromagnets. We stripped off a one-dimensional subset (zigzag ladder) and investigated the phase diagram by a combined use of large-scale numerical simulations and field-theoretical methods.Magnetism of a new two-dimensional spin-gap compound (CuCl)LaNb_2O_7. The Cu-based compound (CuCl)LaNb_2O_7 exhibits a finite spin gap above a singlet ground state and undergoes a spin-Bose-Einstein condensation (BEC) when strong enough field is applied. According to the standard theory of spin-BEC, the observed spin gap and the critical field, at which spin-BEC mass, seem inconsistent with each other. We proposed a new scenario that BEC occurs in spin-quintet channel to explain magnetism of this compound. The most remarkable feature of this new kind of spin-BEC is that the transverse magnetization vanishes even after the onset of magnetization.

在一维量子磁铁中构建统一的理论，用于竞争订单，其中包含多旋转交换相互作用。多旋转交换相互作用（特别是环交换相互作用）的影响本身就引人入胜，因为这些相互作用被认为是许多异国情调量子阶段的潜水hoe。我们从基于高对称性的统一观点中确定了梯形型模型的全局相结构（例如，交错二聚体，交错的标量性手性，nematic等）的全局相结构。我们的分析表明，可以通过考虑带有旋转的有效玻色液体来理解这些系统的基本相结构（s = 1）。我们还通过使用承包商 - 层次化（Core）方法将方法扩展到二维病例。迈向理解Spin-1三角形晶格抗fiferromagnets的基层阶段的第一步。在三角形晶格上发现了新的Spin-1二维抗铁磁铁，这引发了S = 1个三角形晶格抗fiferromagnets的各种地面阶段的兴趣。我们剥离了一维子集（锯齿形梯子），并通过大规模数值模拟和现场理论方法的联合使用研究了相图。基于Cu的化合物（CUCL）LANB_2O_7在单重态基态以上表现出有限的自旋隙，并在应用足够强的场时经历自旋 - 玻璃良-Einstein凝结（BEC）。根据Spin-BEC的标准理论，观察到的自旋隙和临界场似乎彼此不一致。我们提出了一个新的场景，该场景发生在自旋Quintet通道中，以解释该化合物的磁性。这种新型旋转BEC的最显着特征是，即使在磁化发作开始后，横向磁化也会消失。

项目成果

Contractor renormalization approach to unconventional orders in Frustrated spin systems

受挫旋转系统中非常规订单的承包商重整化方法

• 发表时间: 2006
• 作者: K.;Totsuka
• 通讯作者: Totsuka

Ground state and supersolids in spin-l/2 J1-J2 model with a plaquette Structure

具有斑块结构的 spin-l/2 J1-J2 模型中的基态和超固体

• 发表时间: 2007
• 作者: H-T.;Ueda;K.;Totsuka
• 通讯作者: Totsuka

Vortex Berry phases and the magnetization of quantum magnets

涡旋贝里相和量子磁体的磁化

• 发表时间: 2008
• 作者: A. Tanaka;K. Totsuka;and X. Hu
• 通讯作者: and X. Hu

A unifying approach to competing orders in frustrated magnets-from ladder to square lattice",

一种统一的方法来处理受挫磁铁中的竞争秩序——从梯子到方格”，

• 发表时间: 2007
• 作者: A.;Tanaka;K.;Totsuka;X.;Hu;K. Totsuka
• 通讯作者: K. Totsuka

self-dual sine-Gordon模型と量子相転移

自对偶正弦戈登模型和量子相变

• 发表时间: 2007
• 作者: 戸塚圭介;P. Lecheminant
• 通讯作者: P. Lecheminant