Superconductivity is one of the most striking phenomena in condensed matter physics, characterized by the complete disappearance of electrical resistance below a critical temperature. While its fundamental principles are rooted in quantum mechanics, statistical mechanics, and many-body physics, the rapid development of unconventional and high-temperature superconductors has made the field increasingly challenging for newcomers. This book provides an intuitive and coherent introduction to both conventional and unconventional superconductivity, connecting fundamental concepts with modern developments in the field.

The volume begins with the essential properties of superconductors and proceeds through phenomenological approaches, including London, Pippard, and Ginzburg-Landau theories, before introducing microscopic descriptions ranging from BCS theory to strong-coupling and fluctuation-mediated pairing mechanisms. It further examines superconductivity in a broad spectrum of materials, including cuprates, iron-based, heavy-fermion, organic, and hydride superconductors, and discusses current perspectives on room-temperature superconductivity.

Bridging classical foundations and contemporary research, this self-contained text emphasizes the physical intuition and core knowledge required for understanding superconducting phenomena and materials. It serves as a valuable resource for advanced undergraduate students, graduate students, and researchers entering the fields of superconductivity, condensed matter physics, and materials science.

Yoji Koike is an emeritus professor at Tohoku University. He received his Ph.D. from the University of Tokyo in 1980. After his Ph.D. program, he moved to Tohoku University as a research associate at the Institute for Materials Research in 1980, and became an associate professor and professor at the department of applied physics in 1989 and 1996, respectively. He was also a visiting professor at Technische Hochschule Darmstadt in 1993. He retired from Tohoku University in 2018.

His research is involved with condensed matter physics and superconductivity, and particularly focuses on electronic properties in strongly correlated electron systems and thermal conductivity in low-dimensional spin systems. He has published 490 original research articles, 33 review articles and 7 books in Japanese.