Superconducting State

Author(s):  
Vladimir Kresin ◽  
Sergei Ovchinnikov ◽  
Stuart Wolf

For the past almost fifty years, scientists have been trying to explain the phenomenon of superconductivity. The mechanism is the key ingredient of microscopic theory, which was developed by Bardeen, Cooper, and Schrieffer in 1957. The theory also introduced the basic concepts of pairing, coherence length, energy gap, and so on. Since then, microscopic theory has undergone an intensive development. This book provides a very detailed theoretical treatment of the key mechanisms of superconductivity, including the current state of the art (phonons, magnons, plasmons). In addition, the book contains descriptions of the properties of the key superconducting compounds that are of the most interest for science and applications. For many years, there has been a search for new materials with higher values of the main parameters, such as the critical temperature and critical current. At present, the possibility of observing superconductivity at room temperature has become perfectly realistic. That is why the book is especially concerned with high-Tc systems such as high-Tc oxides, hydrides with record values for critical temperature under high pressure, nanoclusters, and so on. A number of interesting novel superconducting systems have been discovered recently, including topological materials, interface systems, and intercalated graphene. The book contains rigorous derivations based on statistical mechanics and many-body theory. The book also provides qualitative explanations of the main concepts and results. This makes the book accessible and interesting for a broad audience.

2021 ◽  
Vol 84 (5) ◽  
pp. 649-659
Author(s):  
S. P. Kamerdzhiev ◽  
M. I. Shitov

Abstract A microscopic model for taking into account quasiparticle–phonon interaction in magic nuclei is considered within nuclear quantum many-body theory. This model is of interest for constructing a microscopic theory of pygmy and giant multipole resonances—first of all, a description of their fine structure. This article reports on a continuation and development of our earlier study [1]. Basic physics results of that study are confirmed here, and new results are obtained: (i) exact (not approximate, as in [1]) expressions for the first and second variations of the vertex in the phonon field are found and employed; (ii) a new equation involving, in addition to the known effective interaction, the total amplitude for particle–hole interaction is derived for the vertex, which is the main ingredient in the theory of finite Fermi systems; (iii) the required two-phonon configurations are obtained owing to the last result. The new equation for the vertex now contains complex configurations such as $$1p1h\otimes\textrm{phonon}$$ and two-phonon ones, along with numerous ground-state correlations.


1987 ◽  
Vol T19A ◽  
pp. 282-288 ◽  
Author(s):  
W van Haeringen ◽  
B Farid ◽  
D Lenstra

We calculate the external incoherent scattering from a finite molecular fluid exposed to a weak, external, coherent electromagnetic field. The scattered field is detected outside the fluid and the system models a real scattering experiment in all its aspects. The analysis is based on a classical all order many-body theory developed in two previous papers. The theory is microscopic, i.e. is developed ab initio and in detail in terms of individual scattering processes in vacuo at a strictly molecular level. But it is shown that the collective action of these generates all of the macroscopic features expected in the external scattering: for example, the refractive index, as it was calculated previously from the many-body theory, plays much of its expected macroscopic role. These macroscopic results are reached by showing that the complete scattering process (from a wave incident in vacuo on the fluid to a wave in vacuo scattered from the fluid) separates into three independent collective processes compactly described by a particular quadrilinear form quadratic in a field $ induced in the fluid by any coherent external field, and quadratic in a ‘weight’ field e describing the scattered field in the fluid. The internal fields $ and e couple separately to the external incoming field and to one representing the external scattered field respectively. In each case they account for all collective surface effects. The kernel of the quadrilinear form accounts for all of the internal scattering processes in the fluid. The weight field e and the equations associated with it describe refraction and (multiple) internal reflection of the scattered light at the surface of the medium in all details: these collective surface effects are managed in a very effective way through a new reciprocity principle derived from the microscopic theory and containing a new form of optical extinction theorem for external scattering. The kernel of the quadrilinear form for internal scattering has a natural expansion describing macroscopic single and macroscopic multiple scattering agreeing with phenomenological ideas. The expansion is derived from a relation between the weight field and a propagator for the scattered wave. We show that macroscopic single scattering contains processes displaying ‘backscattering coherence’. This phenomenon has not been recognized in molecular scattering theory before, and back-scattering enhancement very much like that recently observed in scattering from suspensions of dielectric particles, should be observable near a critical point of phase separation. We give explicit formulae for macroscopic single scattering from a dilute gas up to two-body contributions with intermolecular correlations determined by a LennardJones potential. We also show how Einstein’s phenomenological single scattering formula can be derived from certain microscopic scattering processes of all orders. With a minor qualification the formula is valid in a generalized form up to neglect of terms of order six in the polarizability per unit volume.


1968 ◽  
Vol 111 (1) ◽  
pp. 392-416 ◽  
Author(s):  
K DIETRICH ◽  
K HARA

1970 ◽  
Vol 31 (C4) ◽  
pp. C4-99-C4-104
Author(s):  
T. P. DAS ◽  
C. M. DUTTA ◽  
N. C. DUTTA

1988 ◽  
Vol 88 (12) ◽  
pp. 7791-7798 ◽  
Author(s):  
Leslie J. Root ◽  
Frank H. Stillinger ◽  
Gary E. Washington

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