Magnetic Phase Transitions and Critical Phenomena of Two-Dimensional Systems

二维系统的磁相变和临界现象

• 批准号: 03640334
• 负责人: KAWAMURA Hikaru
• 金额: $ 0.96万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1991
• 资助国家: 日本
• 起止时间: 1991 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03640334/
• 关键词: topological transitions; triangular lattice antiferromagnets; Monte Carlo simulations; chirality; two-dimensional electron systems; Stark ladder; Wigner crystal; Anderson transitions; 量子融解; 2次元素; 繰り込み群; フラストレ-ション; モンテカルロシミュレ-ション; 電子ーリプロン相互作用

Topological phase transitions of two-dimensional systems with vortex excitations are analyzed. As a new type of order parameter of such topological transitions, a vorticity modulus is introduced and its behavior is studied by means of a Monte Carlo sinulation combined with an appropriate type of boundary conditions. Two-Dimensional XY (plane rotator) model, triangular-lattice Heisenberg antiferromagnet and ferromagnetic Heisenberg model are studied and the results are analyzed based on a finite-size scaling theory. In the case of the XY model, the results support a theory proposed by Kosterlitz-Thonless, while in case of triangular antiferromagnets, the results support the occurrence of a finitetemperature topological transition driven by Z_2 -vortices as suggested by Kawamura and Miyashita.Critical properties of triangular-lattice antiferromagnets are studied near two dimensions on the basis of a field theoretic nonlinear sigma model and the renormalization-group epsilon=d-2 expansion. Critical properties of XY and Heisenberg antiferromagnets on a three-dimensional stacked-triangular lattice are also studied directly by extensive Monte Carlo simulations. The estimated exponents and the amplitude ratio are in good agreement with the experimental results.Electron-ripplon interactions in a two-dimensional electron system on liquid helium surface are studied.With a two-dimensional hyperlattice in mind, energy spectrum of tightbinding models under strong magnetic and electric fields are studied.Transport properties of layered electronic systems under strong magnetic fields are studied.

分析了二维涡旋激励系统的拓扑相变。作为这种拓扑转变的一种新的序参量，引入了涡度模量，并通过Monte Carlo模拟结合适当类型的边界条件研究了它的行为.研究了二维XY（平面旋转体）模型、三角格子海森堡反铁磁体模型和铁磁海森堡模型，并基于有限尺寸标度理论对结果进行了分析。在XY模型的情况下，结果支持Kosterlitz-Thonless提出的理论，而在三角形反铁磁体的情况下，结果支持了Kawamura和Miyashita提出的由Z_2 -涡旋驱动的有限温度拓扑转变的发生.基于场论非线性σ模型和重整化方法，研究了三角晶格反铁磁体在二维附近的临界性质.组n =d-2膨胀。通过大量的Monte Carlo模拟直接研究了XY和Heisenberg反铁磁体在三维叠层三角晶格上的临界性质。研究了液氦表面二维电子系统中的电子-ripplon相互作用，考虑二维超晶格，研究了强磁场和电场作用下紧束缚模型的能谱，研究了强磁场作用下层状电子系统的输运性质.

项目成果

H. Kawamura: "Chiral Criticality near Two Dimensions" J. Phys. Soc. Jpn. 60. 1839-1843 (1991)

H. Kawamura：“二维附近的手性临界”J. Phys。

H.KAWAMURA: "Free-Vortex Formation and Topological Phase Transitions of Two-Dimenstional Spin Systems" Phy.Rev.B. (1993)

H.KAWAMURA：“二维自旋系统的自由涡形成和拓扑相变”Phy.Rev.B。

M.KIKUCHI: "Free-Vortex Formation of the Plane Rotator Model" J.Magn.Magn.Mater.104-107. 227-228 (1992)

M.KIKUCHI：“平面旋转器模型的自由涡流形成”J.Magn.Magn.Mater.104-107。

H.KAWAMURA: "Monte Carlo Study of Chiral Ctiticality-XY and Heisenberg Stacked-Triangular Antiferromagnets" J.Phys.Soc.Jpn.61. 1299-1325 (1992)

H.KAWAMURA：“手性临界性-XY 和海森堡堆叠三角形反铁磁体的蒙特卡罗研究”J.Phys.Soc.Jpn.61。

T.Ohtsuki: "Electronic States in disordered layered systems in the quantum Hall regime" Surface Science. 263. 263-265 (1992)

T.Ohtsuki：“量子霍尔体系中无序层状系统中的电子态”表面科学。