共查询到20条相似文献,搜索用时 15 毫秒
1.
《Physics letters. A》1997,235(5):535-539
We study disordered Peierls systems described by the fluctuating gap model. We show that the typical electron states with energies lying deep inside the pseudogap are localized near large disorder fluctuations (instantons), which have the form of a soliton-antisoliton pair. Using the “saddle-point” method we obtain the average density of states and the average optical absorption coefficient at small energy. 相似文献
2.
We have studied the influence of bond- and site-type impurities on the ground state properties of one-dimensional Peierls systems. Using a functional integral formalism with both commuting and anticommuting variables we have calculated the averaged Green's function which determines the electronic density of states and localization length (Thouless formula). Some limiting cases can be solved analytically. To apply our model to doped polymers we derive the connection between doping concentration and disorder strengths Dj. For illustration we present the results with parameters appropriate for polyacetylene. 相似文献
3.
We consider the low-temperature expansion for the Ising model on
, with ferromagnetic nearest neighbor interactions in terms of Peierls contours. We prove that the expansion converges for all temperatures smaller than Cd(log d)–1, which is the correct order in d. 相似文献
4.
An improvement of the Peierls equation has been made by including the lattice effects. By using the
non-trivially gluing mechanism for the simple cubic lattice, in which atoms interact with its first and second nearest neighbours through a central force, the dislocation equation has been derived
rigorously for the isotropic case. In the slowly varying approximation, the Peierls equation with the improvement by including the lattice effects has been obtained explicitly. The new equation can be used to substitute for the old one in theoretical investigations of dislocations. The major change of
the predicted dislocation structure is in the core region. The width of the dislocation given by using the new equation is about three times that given by the classical Peierls--Nabarro theory
for the simple cubic lattice. 相似文献
5.
We consider the static Holstein model, describing a chain of fermions interacting with a classical phonon field, when the interaction is weak and the density is a rational number p = P/Q, with P, Q relative prime integers. We show that the energy of the system, as a function of the phonon field, has one (if Q is even) or two (if Q is odd) stationary points, defined up to a lattice translation, which are local minima in the space of fields periodic with period equal to the inverse of the density. 相似文献
6.
7.
We study the (spin-)Peierls transition in quasione- dimensional disordered systems, treating the lattice classically. The role of kinks, induced thermally and by disorder, is emphasized. For weak interchain interaction the kinks destroy the coherence between different chains at a temperature significantly lower than the mean-field Peierls transition temperature. We formulate the effective Ising model, which describes such a transition, investigate the doping dependence of the (spin-)Peierls transition temperature and discuss several implications of the picture developed. The results are compared with the properties of the spin-Peierls system CuGeO3. 相似文献
8.
9.
10.
Benoit Gars 《哲学杂志》2013,93(11):1390-1421
The effect of a free surface on the Peierls stress of a perfect dislocation, as well as on one of two dislocation partials under a free surface, has been accounted for by considering the Lubarda–Markenscoff variable-core dislocation model (VCM). The VCM dislocation smears the Burgers vector, while producing on the slip plane the Peierls–Nabarro sinusoidal relation between the stress and the slip discontinuity with a variable width. Here the core radius is allowed to depend on the distance to the free surface and the other partial. The Peierls stress is computed as a configurational force by accounting for all the energies and the image stresses to satisfy the traction-free boundary conditions. The results are applied to aluminum and copper and comparisons are made with atomistic calculations in the literature that show that the partials merge as they approach the free surface. 相似文献
11.
12.
用变温电子自旋共振手段,对轨道诱导Peierls相变MgTi2O4体系进行了研究。研究发现,轨道诱导Peierls相变所伴随的自旋二聚相变对ESR谱产生了影响。在相变温度以上,MgTi2O4的磁性为顺磁行为。而在相变温度以下,ESR谱显示MgTi2O4的磁性偏离了顺磁行为。对ESR谱线的参数拟合结果显示,MgTi2O4在发生轨道诱导Peierls相变时,自旋耦合作用逐渐增强。这说明:自旋耦合作用的增强很有可能是导致相变的一个重要的因素。 相似文献
13.
In the classical
Peierls--Nabarro (P-N) theory of dislocation,
there is a long-standing contradiction that the stable configuration
of dislocation has maximum energy rather than minimum energy. In
this paper, the dislocation energy is calculated rigorously in the
context of the full lattice theory. It is found that besides the
misfit energy considered in the classical P-N theory, there is an
extra elastic strain energy that is also associated with the
discreteness of lattice. The contradiction can be automatically
removed provided that the elastic strain energy associated with the
discreteness is taken into account. This elastic strain energy is
very important because its magnitude is larger than the misfit
energy, its sign is opposite to the misfit energy. Since the elastic
strain energy and misfit energy associated with discreteness cancel
each other, and the width of dislocation becomes wide in the lattice
theory, the Peierls energy, which measures the height of the
effective potential barrier, becomes much smaller than that given in
the classical P-N theory. The results calculated here agree with
experimental data. Furthermore, based on the results obtained, a
useful formula of the Peierls stress is proposed to fully include
the discreteness effects. 相似文献
14.
15.
用变温电子自旋共振手段(Electron Spin Resonance,ESR),对轨道诱导Peierls相变MgTi_2O_4体系进行了研究.研究发现,轨道诱导Peierls相变所伴随的自旋二聚相变对ESR谱产生了影响.在相变温度以上,MgTi_2O_4的磁性为顺磁行为.而在相变温度以下,ESR谱显示MgTi_2O_4的磁性偏离了顺磁行为.对ESR谱线的参数拟合结果显示,MgTi_2O_4在发生轨道诱导Peierls相变时,自旋耦合作用逐渐增强.这说明:自旋耦合作用的增强很有可能是导致相变的一个重要的因素. 相似文献
16.
根据建立在电子-声子相互作用基础上的Peierls 相变理论,利用形变势模型和半经验晶体轨道方法计算的能带结构数据,对一维有机导体tetrathiafulvalene-tetracyanoquinodimethane的Peierls相变温度进行了计算.并对其金属-绝缘体相变机制进行了讨论.
关键词:
电子-声子相互作用
Peierls相变温度
一维有机导体 相似文献
17.
H. P. van de Braak W. J. Caspers F. W. Wiegel M. W. M. Willemse 《Journal of statistical physics》1978,18(6):577-584
A renormalization procedure gives a rigorous upper bound for the ground-state energy per spin for a Peierls-distorted antiferromagnetic chain with Heisenberg interaction. 相似文献
18.
We show that, assisted by the Peierls transition of lattice, as a quasi-one dimensional (Q1D) tight binding system, a Möbius molecular device can behave as a simple topological insulator. With the Peierls phase transition to form a domain wall, the solitonary zero modes exist as the ground state of this electron-phonon hybrid system, which is protected by the Z2 topology of the Möbius strip. The robustness of the ground state prevents these degenerate zero modes from their energy spectrum splitting caused by any perturbation. 相似文献
19.
Due to the high anisotropy of the dc conductivity (σ|/σ⊥ ≈ 104) the organic conductor (fluoranthene)2X can be regarded as a model system for studying the Peierls instability in quasi-one-dimensional systems. The temperature dependence of the dc conductivity σ| (T) along the highly conducting crystal axis exhibits the typical behaviour of a quasi-one-dimensional metal with a Peierls transition at about 180 K to a charge density wave (CDW) ground state. As expected for a highly one-dimensional conductor the exact transition temperature depends on three-dimensional coupling effects and therefore on the size of the counterion X? = PF, AsF, SbF. Above the Peierls transition σ| (T) can be described quantitatively within a model of CDW fluctuations leading to a pseudo gap in the electronic density of states. Below, the existence of a real energy gap at the Fermi level with a BCS-like temperature dependence determines the charge transport over more than eight orders of magnitude in the electrical resistance. For the intrinsic energy gaps 2 Δ (0), which characterize the ground state of the Peierls semiconductor, values of 120-180 meV have been found for different crystals. 相似文献
20.
We prove identities between integrated Ursell functions and derivatives of the pressure in the thermodynamic limit, for multicomponent classical spin systems which obey the Lee-Yang theorem and some form of Gaussian domination, when the susceptibility is finite (T>T
c). Following Refs. 3 and 4, we view the moment generating function of the magnetization as the inverse of an infinitely divisible characteristic function. Fluctuation susceptibility relations of all orders then follow by bounding the corresponding cumulants, taken in zero external field. High-order cumulants are bounded in terms of the susceptibility using Gaussian and Simon's inequalities for short-range interactions. 相似文献