Quantum Monte Carlo Study on Strongly Quantum Fluctuated Systems

强量子涨落系统的量子蒙特卡罗研究

• 批准号: 08640485
• 负责人: MIYASHITA Seiji
• 金额: $ 1.66万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640485/
• 关键词: quantum phase transition; singlet pair; quantum Monte Carlo method; quantum fluctuation; itinerant ferromagnetism; flutband

Systems with strong quantum fluctuation due to the stracture of lattice in order to find new peculiar properties.The effects due to the structure of the lattice on the ordering configuration in the Heisenberg antiferromagnets are investigated. Ordering configuration means the configuration of singlet bonds which is classified with the VBS picture. In particular we investigated a chain which consists of two of S=1 spins and two of S=1/2 spins.We also investigated effects of inhomogeneity on quantum mechanical order : effects of impurities of S=1/2 spins, and effects of dilution on the lader lattice and square lattice. In the latter project, we find so-called quantum Criffiths phase where the any correlation in the spatial direction decays exponentially but the correlation in the time axis diverges. This divergence causes the divergence of the local susceptibility.We studied a new phase due to the quantum fluctuation in the magnetization curve in the ground state of antiferromagnetic Heisenberg model with XY anisotropy. There a collinear configuration which is unfavorite in classical case becomes stable. The transition is clearly observed by investigating the wavefunction although the transition is not clear in the changes of physical quantities.We investigated the low temperature properties of quantum spin systems by quantum Monte Carlo method and transfer matrix method.We found a new mechanism of the ferromagnetism in the Hubbard model and analyzed the nature of the ferromagnetism.We started to study the dynamics of system where the quantum fluctuation has a dominant role.

研究了晶格结构对Heisenberg反铁磁体有序位形的影响。有序构型是指单重键的构型，它是按照VBS图分类的。特别地，我们研究了由两个S=1自旋和两个S=1/2自旋组成的链，还研究了非均匀性对量子力学序的影响：S=1/2自旋杂质的影响，以及稀释对梯形晶格和正方形晶格的影响。在后一个项目中，我们发现了所谓的量子Criffiths阶段，在空间方向上的任何相关性呈指数衰减，但在时间轴上的相关性发散。我们研究了XY各向异性反铁磁海森堡模型基态磁化曲线中由于量子涨落而产生的新相位。一个在经典情况下不受欢迎的共线构型变得稳定。虽然在物理量的变化上还不清楚，但通过波函数的研究可以清楚地观察到这种转变。我们用量子Monte Carlo方法和转移矩阵方法研究了量子自旋系统的低温性质。在Hubbard模型中发现了一种新的铁磁性机制，并分析了铁磁性的本质。我们开始研究量子涨落具有一定作用的系统的动力学。我们还研究了量子自旋系统的动力学性质。一个主导的角色。

项目成果

M.Yamanaka,M.Oshikawa & S.Miyashita: "Hidden Order and Dimerization Transition in S=2 Chain" J.Phys.Soc.Jpn.65・6. 1562-1565 (1996)

M.Yamanaka、M.Oshikawa 和 S.Miyashita：“S=2 链中的隐藏顺序和二聚化转变”J.Phys.Soc.Jpn.65・6（1996）。

S.Miyashita: "Nature of the Ordered Phase and the Critical Properties of the Three Dimensional Six-state Clock Model" J.Phys.Soc.Jpn.66. 3411-3420 (1997)

S.Miyashita：“有序相位的本质和三维六态时钟模型的关键属性”J.Phys.Soc.Jpn.66。

S.Miyashita, K.Saito and H.De Raedt: "Nontrivial resonance of nanoscale uniaxial magnets to alternating field" Phys.Rev.Lett.80. 1525-1528 (1998)

S.Miyashita、K.Saito 和 H.De Raedt：“纳米级单轴磁体对交变场的非​​平凡共振”Phys.Rev.Lett.80。

T.Tonegawa, T.Hikihara, M.Kaburagi, T.Nishino, S.Miyashita and H.-J.Mikeska: "One-Dimensional Heisenberg Anfiferromagnets in which two S=1/2 and two S=1 spins are arranged alternatively" J.Mag.Mag.Matt.(1997)

T.Tonekawa、T.Hikihara、M.Kaburagi、T.Nishino、S.Miyashita 和 H.-J.Mikeska：“一维海森堡反铁磁体，其中两个 S=1/2 和两个 S=1 自旋交替排列

S.Takagi & G.Tatara: "Macroscopic quantum coherence of chirality of a domain wall in ferromagnets" Phys.Rev.B54・14. 9920-9922 (1996)

S.Takagi & G.Tatara：“铁磁体中磁畴壁手性的宏观量子相干性”Phys.Rev.B54・14（1996）。