Theory Of Quantum Liquids: Superfluid Bose Liquids PDF

Preface

Our aim in writing this book has been to provide a unified, yet elementary. account of the theory of quantum liquids. Strictly speaking, a quantum liquid is a spatially homogeneous system of strongly interacting particles at temperatures sufficiently low that the effects of quantum statistics are important. In this category fall liquid ³He and ⁴He. In practice, the term is used more broadly, to include those aspects of the behavior of conduction electrons in metals and degenerate semiconductors which are not sensitive to the periodic nature of the ionic potential. The conduction electrons in a metal may thus be regarded as a normal Fermi liquid, or a superfluid Fermi liquid, depending on whether the metal in question is normal or superconducting.

While the theory of quantum liquids may be said to have had its origin some twenty-five years ago in the classic work of Landau on ⁴He, it is only within the past decade that it has emerged as a well-defmed subfield of physics. Thanks to the work of many people, we possess today a unified point of view and a language appropriate for the description of many-particle systems. We understand where elementary excitations afford an apt description and where they do not; we appreciate the relationship between quasiparticle excitations and collective modes, and how both derive from the basic interactions of the system particle. There now exists a number of model solutions for the many-body problem, solutions which can be shown to be valid for a given class of particle interactions and system densities: examples are an electron system at high densities and low temperatures, and a dilute boson system at low temperatures. In addition, there is a semiphenomenological theory, due to Landau, which describes the macroscopic behavior of an arbitrary normal Fermi liquid at low temperatures. Finally, and most important, has been the development of a successful microscopic theory of superconductivity by Bardeen, Cooper, and Schrieffer.

Author: Philippe Nozieres