1992 Fiscal Year Final Research Report Summary
Magnetic Phase Transitions and Critical Phenomena of Two-Dimensional Systems
| Project/Area Number |
03640334
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物性一般（含極低温･固体物性に対する理論）
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| Research Institution | Osaka University |
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Principal Investigator |
KAWAMURA Hikaru Osaka University, College of General Education, Associate Professor, 教養部, 助教授 (30153018)
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| Co-Investigator(Kenkyū-buntansha) |
OHTSUKI Tomi Osaka University, College of General Education, Assistant, 教養部, 助手 (50201976)
SAITOH Motohiko Osaka University, College of General Education, Professor, 教養部, 教授 (80012441)
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| Project Period (FY) |
1991 – 1992
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| Keywords | topological transitions / triangular lattice antiferromagnets / Monte Carlo simulations / chirality / two-dimensional electron systems / Stark ladder / Wigner crystal / Anderson transitions |
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| Research Abstract |
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.
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