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1.
The influence of the intrachain Coulomb interactions on the Peierls transition is examined. The change of the form of the electronic polarizability at twice the Fermi wavevector, to a power law divergence in the presence of Coulomb interactions, is found to enhance the mean field transition temperature for the Peierls transition. 相似文献
2.
J.R. Cooper J. Lukatela M. Miljak J.M. Fabre L. Giral E. Aharon-Shalom 《Solid State Communications》1978,25(9):699-704
Conductivity measurements on isotopically substituted single crystals of TTF-TCNQ show a relatively large shift in the phase transition temperatures at 52.5 K (T1) and 37.7 K (T3). Deuteration of both TTF and TCNQ chains increases T1 by 0.75 ± 0.15 K, N15 substitution increases T1 by 0.6 ± 0.1 K while deuteration of the TTF chains apparently has no significant effect. Different possible interpretations of these results are briefly discussed. 相似文献
3.
4.
Y. Ono 《Solid State Communications》1978,28(9):763-765
The impurity concentration dependence of the transition temperature into the Peierls phase is discussed in the low concentration region (i.e. in the linear region), assuming a δ-function type potential. The effect of fluctuation is taken account of by the method of Scalapino, Sears and Ferrell. The decrease of the transition temperature per one per cent of impurities is estimated in the case of TTF—TCNQ but found to be one order of magnitude smaller than that observed recently in an experiment. 相似文献
5.
J.R. Cooper J. Lukatela M. Miljak J.M. Fabre L. Giral E. Aharon-Shalom 《Solid State Communications》1978,25(11):949-954
Conductivity measurements on isotopically substituted single crystals of TTF-TCNQ show a relatively large shift in the phase transition temperatures at 52.5 K (T1) and 37.7 K (T3). Deuteration of both TTF and TCNQ chains increases T1 by 0.75 ± 0.15 K, N15 substitution increases T1 by 0.6±0.1 K while deuteration of the TTF chains apparently has no significant effect. Different possible interpretations of these results are briefly discussed. 相似文献
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7.
Summary In long molecules with helical structure it is shown that the electron’s response functionF(q,T) is singular for various wave vectors. Then deformed phases associated with different periodicites can occur as a function
of external pressure. The calculation was done as a function of temperature and for small number of atoms per turn.
Riassunto Si mostra in lunghe molecole con struttura elicoidale che la funzione di risposta dell’elettroneF(q, T) è singolare per vari vettori d’onda. Allora possono verificarsi fasi deformate associate a diverse periodicità in funzione della pressione esterna. Si effettua il calcolo in funzione della temperatura e per un numero ridotto di atomi per spira.
Резюме В длинных молекулах с геликоидальной структурой показывается, что функция электронного откликаF(q, T) является сингулярной для различных волновых векторов. В связи с этим могут возникать деформированные фазы, связанные с различными периодичностями, в зависимости от внешнего давления. Проводятся вычисления в зависимости от температуры и для малого числа атомов на виток.相似文献
8.
We use the density matrix renormalization group method to investigate the role of longitudinal quantized phonons on the Peierls transition in the spin-Peierls model. For both the XY and Heisenberg spin-Peierls model we show that the staggered phonon order parameter scales as sqrt[lambda] (and the dimerized bond order scales as lambda) as lambda-->0 (where lambda is the electron-phonon interaction). This result is true for both linear and cyclic chains. Thus, we conclude that the Peierls transition occurs at lambda=0 in these models. Moreover, for the XY spin-Peierls model we show that the quantum predictions for the bond order follow the classical prediction as a function of inverse chain size for small lambda. We therefore conclude that the zero lambda phase transition is of the mean-field type. 相似文献
9.
We propose two simplified models in order to discuss the origin of the Peierls transition in one-dimensional systems. For the finite-mode model we show that the thermodynamic properties are described correctly by the most general mean field approximation. But the discussion of the zero-bandwidth model suggests that this result is probably due to the fact of taking into account only a finite number of phonon modes even in the thermodynamic limit. 相似文献
10.
The properties of a one-dimensional conductor in the presence of an external periodic potential VQ have been investigated. The low temperature gap is enhanced, the temperature dependence of the gap Δ(T) is smeared at TPF, the Peierls transition temperature in the absence of VQ, and hence there is no longer a real phase transition. We also relate the phase pinning frequency ωø to the size of VQ. 相似文献
11.
We consider the continuum approximation of a half-filled site-disordered Fröhlich chain in the mean-field approximation. We perform the configurational average over Gaussian-distributed and short-range-correlated potentials by means of the supersymmetry method and obtain an exact analytic formula for the integrated density of states containing many previously known special cases. It enables the minimization of the ground state energy with respect to the Peierls order parameter which is calculated in dependence on two disorder parameters describing forward and umklapp scattering. The Peierls transition proves to be continuous and takes place even if the density of states diverges at the Fermi energy, which eventually happens if only umklapp scattering is present. 相似文献
12.
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
13.
The exact solution of the problem of the ground state of theXY-spin system on a deformed chain is found. At finite magnetizationm it is characterized by the double periodic structure and has a finite-band spectrum of spin excitations. Atm 0 the phase transition from the incommensurate into the dimerized state is accompanied by the soliton lattice formation. 相似文献
14.
J.W. Bray 《Solid State Communications》1978,26(11):771-773
We consider the effect of a magnetic field on the spin—Peierls transition within mean-field theory. Using a mathematical analogy to the regular Peierls transition and existing results, we derive formulas for the magnetic field dependence of the transition temperature and of the distortion periodicity. 相似文献
15.
G. Beni 《Solid State Communications》1974,15(2):269-272
We study the thermodynamics of a noninteracting electron system with a half filled strongly anisotropic tight binding band in the mean field approximation. This system may exhibit a structural transition dimerizing along the high conductivity direction. The conditions for the instability to occur are given as a function of the degree of anisotropy. The relationship to the behavior of TCNQ salts is discussed. 相似文献
16.
S. Chatterjee 《Solid State Communications》1984,50(8):773-776
The stability of the Peierls phase is investigated in the presence of a radiation with frequency less than that for inter-band transitions. It is observed that such an external radiation enhances the gap. This result is in contrast with the case when the external radiation has a frequency higher than that for inter-band transitions. 相似文献
17.
We present the first derivation of the analytic expression for the Peierls-Nabarro potential for crowdion migration using the double sine-Gordon model. The analysis is guided by the group-specific trend in the shapes of the periodic lattice potentials calculated for the body-centered-cubic transition metals in groups 5B and 6B of the periodic table. We combine density-functional calculations of the crowdion's profile and environment with an extended version of the analytical Frenkel-Kontorova model, and determine the effective potential experienced by the defect's center of mass. This reveals important underlying differences between the metals in these groups, which are inaccessible to either the numerical or analytical approaches alone, and accounts for the previously unexplained significantly higher crowdion migration temperatures observed in the metals of group 6B relative to those of group 5B. 相似文献
18.
W. Dieterich 《Solid State Communications》1975,17(4):445-449
The dynamic structure factor near the Peierls instability in weakly coupled metallic chains is examined. Treating the conduction electrons in the adiabatic approximation, an effective anharmonic ion-Hamiltonian is constructed, the dynamic properties of which are studied by using a moment method. We discuss the occurrence of a central peak near the onset of three-dimensional ordering and the temperature dependence of the phonon frequencies in the vicinity of the Kohn anomaly. Qualitative agreement with neutron scattering experiments on KCP is obtained. 相似文献
19.
We report on the reflectance of blue bronze crystals in the visible frequency range as a function of temperature. The observed large oscillations in the reflectance at all wavelengths at temperatures near the Peierls transition are interpreted as interference effects stemming from a surface layer. It is found that the surface layer, which appears to be tied to fluctuations, can be as much as 1.6 microns thick. 相似文献