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Peierls Transition and Phonon Softening in 2D Electron-Lattice System

二维电子晶格系统中的 Peierls 跃迁和声子软化

基本信息

批准号：
16540329
负责人：
ONO Yoshiyuki
金额：
$ 1.73万
依托单位：
Toho University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

The Fermi surface (line) of a 2D electron system with a half-filled band is square-shaped. This fact makes us expect the Peierls transition in the presence of the electron-lattice interaction, similarly as in 1D systems. In order to clarify the ground state of the 2D electron-lattice system, we have studied numerically the lattice distortions minimizing the total energy of the system. It is found that the Fourier components of the lattice distortion in the ground state involve not only the nesting vector of the Fermi line but also many other wave vectors parallel to it. We call this state the multimode Peierls (MMP) state. When the temperature is lowered from the high temperature region, the phonon modes with the nesting vector and with those parallel to it are softened due to the interaction between the electrons and the phonons, all at the same critical temperature. This is consistent with the structure of the ground state at lower temperatures.In real systems, there are many effects … More not included in the ideal electron-lattice model, such as anisotropy and electron-electron interactions. By performing detailed numerical works, we have shown that, even in the presence of anisotropy, the MMP state survives as the lowest energy state at the low temperature limit as long as the anisotropy parameter is around a few per cent or below. Nevertheless, a finite anisotropy changes the phonon softening behavior in the vicinity of the critical temperature; namely, the frequency of the nesting vector mode vanishes first as lowering the temperature, which means that the single-mode Peierls (SMP) state is realized just below the critical temperature. Further lowering the temperature leads to the 1st order phase transition from the SMP state to the MMP state at the second critical temperature. The phase diagram in the presence of the anisotropy becomes very complicated.As for the electron-electron interaction, it has been argued that the MMP state is the lowest energy state as long as the electron interaction parameter lies within the weak coupling region, based on the numerical calculations using the so-called Peierls- Hubbard model. The increase of the Hubbard parameter induces a quantum phase transition from the MMP state to the antiferromagnetic spin-density wave (SDW) state. It is confirmed that the coexistence of the MMP state and the SDW state as a uniform phase does not occur. In the strong correlation limit the model is mapped onto the antiferromagnetic spin-Peierls model. In this model, we have found the 1^<st> order type transition from the SDW state to the multimode spin-Peierls state as the spin- lattice coupling is increased exceeding a certain critical value.We can control the ground state of the 2D electron-lattice system by changing slightly the system parameters, and therefore this system would be useful to study a variety of properties, e.g. in organic conductors. This study will open a way to wide applications. Less

具有半填充带的二维电子系统的费米面（线）是正方形的。这一事实使我们期待在电子-晶格相互作用的存在下的Peierls转变，类似于在1D系统中。为了阐明二维电子-晶格系统的基态，我们数值研究了使系统总能量最小的晶格畸变。研究发现，基态晶格畸变的傅里叶分量不仅涉及费米线的嵌套矢量，还涉及许多与费米线平行的其他波矢量，我们称这种状态为多模Peierls（MMP）态。当温度从高温区域降低时，由于电子和声子之间的相互作用，具有嵌套矢量的声子模和与其平行的声子模都在相同的临界温度下软化。这与较低温度下基态的结构是一致的。在真实的系统中，有很多效应 ...更多信息不包括在理想的电子-晶格模型，如各向异性和电子-电子相互作用。通过进行详细的数值计算，我们已经表明，即使在各向异性的存在下，MMP状态的生存作为最低的能量状态在低温极限，只要各向异性参数是百分之几或以下。然而，有限的各向异性改变了声子软化行为在附近的临界温度，即，嵌套矢量模式的频率消失的第一个作为降低温度，这意味着单模Peierls（SMP）的状态是实现的临界温度以下。进一步降低温度导致在第二临界温度下从SMP状态到MMP状态的一级相变。对于电子-电子相互作用，根据Peierls-Hubbard模型的数值计算，认为只要电子相互作用参数在弱耦合区，MMP态是最低能态。随着Hubbard参数的增加，量子相变从MMP态向反铁磁自旋密度波（SDW）态转变。证实了MMP状态和SDW状态作为均匀相的共存不发生。在强关联极限下，该模型被映射到反铁磁自旋Peierls模型。在这个模型中，我们发现<st>当自旋-晶格耦合超过某一临界值时，从SDW态到多模自旋-Peierls态的1阶型跃迁，我们可以通过改变系统参数来控制二维电子-晶格系统的基态，因此这个系统将有助于研究各种性质，例如有机导体.本研究为该技术的广泛应用开辟了一条道路。少

项目成果

期刊论文数量（43）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

BOW-SDW Transition in the Two-Dimensional Peierls-Hubbard Model

二维 Peierls-Hubbard 模型中的 BOW-SDW 转变

DOI：
发表时间：
2004
期刊：
J. Phys. Soc. Jpn. 73
影响因子：
0
作者：
Y.Ono;S.Chiba;T.Hamano;Yoshiyuki Ono;Shutaro Chiba;Tetsuya Hamano;Shutaro Chiba;Shutaro Chiba
通讯作者：
Shutaro Chiba

Phonon Dispersion Relations in Two-Dimensional Peierls Phase

二维 Peierls 相中的声子色散关系

DOI：
发表时间：
2004
期刊：
J. Phys. Soc. Jpn. 73
影响因子：
0
作者：
Y.Ono;S.Chiba;T.Hamano;Yoshiyuki Ono;Shutaro Chiba;Tetsuya Hamano;Shutaro Chiba
通讯作者：
Shutaro Chiba

2D Peierls State in a Square Lattice - Effect of Anisotropy

方形晶格中的二维 Peierls 态 - 各向异性的影响

DOI：
发表时间：
2005
期刊：
Synthetic Metals 152
影响因子：
0
作者：
Y.Ono;S.Chiba;T.Hamano
通讯作者：
T.Hamano

Two-Dimensional Spin-Peierls State With a Multimode Lattice Distortion

具有多模晶格畸变的二维自旋 Peierls 态

DOI：
发表时间：
2006
期刊：
J. Phys. Soc. Jpn. 75
影响因子：
0
作者：
H Kadowaki;A Nishiyama;K Matsuda;Y Maniwa;S Suzuki;Y Achiba;H Kataura;Shutaro Chiba
通讯作者：
Shutaro Chiba

Phonon Softening and Multimode Peierls Transition in a 2D Anisotropic Square-Lattice Electron-Lattice System with a Half-Filled Electronic Band

半充满电子能带二维各向异性方晶格电子晶格系统中的声子软化和多模 Peierls 跃迁