STRONG COUPLING THEORY OF IMPURE SUPERCONDUCTORS: REAL SPACE FORMALISM

Pair breaking in strong-coupling superconductors

Functional Strong Coupling Theory

The vacuum expectation value of the S-matrix is represented, following HORI, as a functional integral and separated according to 5Vac = exp( — i W) f D (p exp( —i / d x L w ) . Now, the functional integral involves only the part L w of the Lagrangian without derivatives and can be easily calculated in lattice space. We propose a graphical scheme which formalizes the action of the operator r = /...

Insulating state of granular superconductors in a strong-coupling regime

We analyze the possibility of the formation of a magnetic-field-induced insulating state in a two-dimensional granular superconductor with relatively strong intergranular coupling and show that such a state appears in a model with spatial variations of the single-grain critical magnetic field. This model describes realistic granular samples with a dispersion in grain sizes and explains the mech...

Are the New High Temperature Superconductors Strong Coupling Systems?*

Under certain circumstances the excitations of a superconductor will not be those predicted by BCS theory, but rather electron bag states. A variational calculation is used to establish this regime in which such collective states form. The fact that such bags may bind more than one electron implies the existence of more than one peak in the plots of dl/dV versus Vp obtained in Giaver tunneling ...

Strong-coupling Theory of High-temperature Superconductivity

High-temperature superconductivity has transformed the landscape of solid state science, leading to the discovery of new classes of materials, states of matter, and concepts. However, despite being over a quarter of a century since its discovery, there is still no single accepted theory to explain its origin. This book presents one approach, the strong-coupling or bipolaron theory, which propos...