Geometrical Frustration in Strongly Correlated Electron Systems
| Project/Area Number |
14540356
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
物性一般(含基礎論)
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| Research Institution | Kyoto University |
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Principal Investigator |
FUJIMOTO Satoshi Kyoto University, Department of Physics, Research Associate, 大学院・理学研究科, 助手 (10263063)
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| Co-Investigator(Kenkyū-buntansha) |
IKEDA Hiroaki Kyoto University, Department of Physics, Research Associate, 大学院・理学研究科, 助手 (90311737)
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| Project Period (FY) |
2002 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2002: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | spin liquid / triangular Heisenberg model / renormalization group / 磁性 / フラストレーション / 超伝導 / 重い電子系 / 量子1次元系 / 近藤効果 / 幾何学的フラストレーション / パイロクロア / 金属絶縁体転移 / 量子1次元素 / 共形場理論 / 電荷秩序 / くりこみ群 |
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| Research Abstract |
Study on low-energy properties of two-dimensional quantum triangular Heisenberg model
Recently, Shimizu et al. reported that in an organic Mott insulator with spin $s=1/2$ on a triangular lattice, κ-(ET)2Cu2(CN)3, no magnetic LRO is observed down to 32 mK. Their experimental results suggest the possibility of a new kind of a ground state including the spin liquid. Subsequently, Nakatsuji et al. found that in a quasi-2D quantum triangular HAF with $s=1$, NiGa2S4, there is no sign of LRO down to 0.35 K, in spite of the existence of strong anferromagnetic interactions. In the latter system, the specific heat coefficient C shows the quadratic-temperature dependence at sufficiently low temperatures, and the uniform spin susceptibility is constant in the low temperature regions, indicating the existence of low-lying massless excitations. The origin of these unexpected low-temperature behaviors has not yet been explained.
Motivated by these experimental results, we have explored low temperature properties of quantum triangular Heisenberg antiferromagnets in two dimension in the vicinity of the quantum phase transition at zero temperature. Using the effective field theory described by the O(3)×O(2) matrix Ginzburg-Landau-Wilson model and the non-perturbative renormalization group method, we chave larified how quantum and thermal fluctuations affect long-wavelength behaviors in the parameter region where the systems exhibit a fluctuation-driven first order transition to a long-range ordered state. We have shown that at finite temperatures the crossover from a quantum Φ^6 theory to a renormalized two-dimensional classical nonlinear sigma model region appears, and in this crossover region, massless fluctuation modes with linear dispersion spin waves govern low-energy physics.
Our results are partly in good agreement with the recent experimental observations for the two-dimensional triangular Heisenberg spin system, NiGa2S4.
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Report
(5 results)
Research Products
(15 results)
