Superfluidity – and closely related to it, superconductivity – are very general phenomena that can occur on vastly different energy scales. Their underlying theoretical mechanism of spontaneous symmetry breaking is even more general and applies to a multitude of physical systems. In these lecture notes, a pedagogical introduction to the field-theory approach to superfluidity is presented. The connection to more traditional approaches, often formulated in a different language, is carefully explained in order to provide a consistent picture that is useful for students and researchers in all fields of physics. After introducing the basic concepts, such as the two-fluid model and the Goldstone mode, selected topics of current research are addressed, such as the BCS-BEC crossover and Cooper pairing with mismatched Fermi momenta.

This book covers main properties of the excitation spectrum in superfluid 4He and the thermodynamics determined by the spectrum. It deals with hydrodynamics and describes that quantitative results should be insignificantly modified with processes of phonon decay taken into account.

This textbook series has been designed for final year undergraduate and first year graduate students, providing an overview of the entire field showing how specialized topics are part of the wider whole, and including references to current areas of literature and research.

This book reports on the latest developments in the field of Superfluidity, one of the most fundamental, interesting, and important problems in physics, with applications ranging from metals, helium liquids, photons in cavities, excitons in semiconductors, to the interior of neutron stars and the present state of the Universe as a whole.

These notes have appeared as a result of a one-term course in superfluidity and superconductivity given by the author to fourth-year undergraduate students and first-year graduate students of the Department of Physics, Moscow State University of Education. The goal was not to give a detailed picture of these two macroscopic quantum phenomena with an extensive coverage of the experimental background and all the modern developments, but rather to show how the knowledge of undergraduate quantum mechanics and statistical physics could be used to discuss the basic concepts and simple problems, and draw parallels between superconductivity and superfluidity.

Superfluidity is the jewel in the crown of low temperature physics. When temperatures are low enough, every substance in thermal equilibrium must become ordered. Since some materials remain fluid to the lowest temperatures, it is a fascinating question as to how this ordering can take place. One possibility is the formation of a superfluid state, a state in which there is macroscopic quantum order-effectively quantum mechanics in a tea-cup. The author develops and presents these ideas in the beginning of Basic Superfluids. The book assumes some basic knowledge of quantum, statistical and thermal physics, and builds on this background to give a readable introduction to the three superfluids of low temperature physics. A short chapter describing experimental techniques is included. The emphasis throughout is on physical principles rather than technical detail, with the aim of introducing the subject in an accessible yet authoritative way to final-year undergraduates or starting postgraduate students.