Vol. 27, No. 1 (1978)
1978, 158 (1): 1-9. doi: 10.7498/aps.27.1
Utilizing the method of optical diffraction produced by acousto-optical interac-tion, we have studied both surface and bulk acoustic waves from the optical diffraction patterns or the inverse phase velocity surfaces excited by interdigital transducers in quartz, with special emphasis on these waves produced in the z-cut crystal. A SAW different from normal Rayleigh waves has been found. On the ground of a brief discussion, we conclude that in many aspects the nature of this wave and/or similar wave disturbances is worthy for further investigations.
INVESTIGATION ON THE EXPONENTIAL FACTOR OF Ic-VBE CHARACTERISTICS OF TRANSISTOR AT LOW INJECTION LEVEL
1978, 158 (1): 10-21. doi: 10.7498/aps.27.10
In this paper, we discuss the various factors affecting the Ic-VBE characteristics of a transistor in the low injection level, i.e. the factors to change n*≡ d(VBE/VT)/dlnIc to departe from 1. It is described also an accurate differential method of measuring n* for integrated transistor-pair. We show that the quasi-Fermi potential drop in emitter junction is an important factor in the explaination on the case n*< 1 observed in some transistors.
1978, 158 (1): 22-30. doi: 10.7498/aps.27.22
In this article, we present a theoretical analysis of the thermal distortion induced by optical pumping in Nd-Glass. Relations between the thermal distortion and the thermo-optical properties of Nd-glass are given. The thermal distortions are measured quantitatively with high repetition frequency and single pulse devices. The experimental results obtained are in agreement reasonably with the theory.
PHYSICAL METHODS OF GROUP REPRESENTATION THEORY (Ⅲ)——OUTER-PRODUCT REDUCTION COEFFICIENTS OF THE PERMUTATION GROUP AND CG COEFFICIENTS OF THE SUn GROUP
1978, 158 (1): 31-40. doi: 10.7498/aps.27.31
This paper introduces an important coefficient-the outer-product reduction coef-ficient of the permutation group (Abbrev as ORC). Its properties and calculation method are discussed. An important relation between the ORC and the CG coeffi-cient of the SUn group is revealed which enables one to derive the latter from the former immediatelv.
AN IONIC GROUPING THEORY OF THE ELECTRO-OPTICAL AND NON-LINEAR OPTICAL EFFECTS OF CRYSTALS (IV)——THE CALCULATION OF LINEAR OPTICAL SUSCEPTIBILITIES IN CRYSTALS OF THE PEROVSKITE AND THE TUNGSTEN BRONZE STRUCTURE TYPES
1978, 158 (1): 41-46. doi: 10.7498/aps.27.41
A localized molecular orbital treatment based on an anion coordination octahedron model has been extended to a systematic calculation on the refractive indices of crystals (9 in all) of the perovskite and the tungsten bronze structure types (without in-troducing any adjustable parameters.) It is found that agreement with experimental data is fairly satisfactory while the deviation is ca. 10 percent. As a straightforward ccnsequence to these calculations, we have been able to elucidate the mechanism of the electro-optical and the non-linear optical effects in crystals of these two structure types and give a good estimate of various properties associated with the linear optical susceptibilities within the range of optical frequencies. In addition, it is shown that although the odd-ordered term drystal field is the decisive factor in the electro-optical and the non-linear optical effects, its contribution to the linear optical susceptibilities is, however, rather small. Finally, a brief discussion is made as to the feasibility of the localized molecular orbital method in the treatment of certain problems in the theory of solid state physics.
1978, 158 (1): 47-62. doi: 10.7498/aps.27.47
An analytical expression for the partition function of the 3-dimensional Ising Model is obtained (see formula (32)). It is approximate, but has several rational features: (1) It is valid on the whole temperature range from zero to infinity and has only one singular point at uc = 0.2612 in comparision to 0.22 from the series expan-sion; (2) It leads to a nonlogarithmic singularity for the specific heat; (3) It can be reduced into the exact Onsager 2-dimensional solution for planar rectangle lattice in the anisotropic case (see formula (34)) ; (4) It has a high temperature expansion, the first two coefficients are correct and the higher ones diminish systematically but remain positive.
ON THE THEORY OF SECOND ORDER PHASE TRANSITION AND AN EXPOSITION ON THE NON-VALIDITY OF LIFSHITZ CONDITION
1978, 158 (1): 63-84. doi: 10.7498/aps.27.63
We assume that the free energy of the system is a functional of order parameter. In the vicinity of second order transition, the free energy density can be expanded as a power series of order parameter as well as its correlation term. Following the pro-cedure given here, for both local and non-local, the order parameter representing equilibrium configuration can be found from the vanishment of the first variation of free energy. In order to find out the solution, it is necessary to carry out Fourier transform for order parameter, and this is identical to expand the order parameter in terms of the base functions of symmetric group of the system. In this way, we analyse the change of symmetry in second order transition.By making use the necessary and sufficient condition (or sufficient condition) for extrema in the variational procedure, the condition of stability for states in second order transition is discussed. Because the correlation term has not been neglected in the procedure of finding extrema, so that the restrictions condition of Lifshitz on sym-metry changing does not come into being. It should be pointed out that, in Lifshitz approach the correlation term is neglected in obtaining the minimum of free energy functional, whereas it is included in discussing the problem of stability. Therefore, Lifshitz's approach is inconsistent in itself. Furthermore, there exists certain kinds of system (such as one component axial vector system), in which the correlation term that leads to the Lifshitz condition cannot be constructed from order parameter. Nevertheless, Lifshitz and others also put restrictions on such system. This is obviously unreasonable. By making use the general theoretical approach described above, we explain the experimental results of phase transition in heavy lanthanide metals at Neel point. It serves as an example to show that there are second order phase transition phenomena for which Lifshitz's approach fails to explain.
1978, 158 (1): 85-93. doi: 10.7498/aps.27.85
In a previous paper (I), we have derived a rigorous series expression for the superconducting critical temperature Tc. Here we discuss the region of convergence of this series, and the possibility of its extension through analytical continuation. Our conclusion is that the above mentioned series or its analytical extension is convergent within the whole region ∞ >λ>λ0. By λ0 we mean the smallest value of λ which can be taken such that the equation determining Tc in the Matsubara representation has a real positive solution. It is in fact the Coulomb pseudopotential. Therefore, ex-cluding possibly a few very weakly coupled ones, our Tc formula is applicable to all superconductors.
1978, 158 (1): 94-106. doi: 10.7498/aps.27.94
The Bethe-Salpeter equation for bound states of a spinor straton-antistraton pair is discussed under the assumption that the interaction between the straton-antistraton pair is purely scalar and may be described by a relativistically covariant v-potential. The structure wave function of the meson is expanded according to the O(4) group, and solved numerically first by keeping the lowest partial waves, and then the in-fluence of the higher partial waves are considered. Numerical results of the wave functions are given both in the momentum space and configuration space, and the mean square radius of the meson is evaluated. It is shown that the low partial wave-large component approximation is valid for tightly bound systems. As a comparison, the loosely bound systems are also discussed.