An object may exhibit properties that are completely different from the properties of the elements that compose it. This is due to the interaction of the elements with each other and is called the many-body effect. For example, superconductivity is a phenomenon in which a large number of electrons interact and cancel each other’s spins, resulting in quantum mechanical waves in phase. This behavior cannot be understood by studying the properties of a single electron, but only by considering it as the result of a large number of electrons.
It was once believed that all of nature could be understood through the study of the components of matter, which could be broken down into molecules, molecules into atoms, atoms into nuclei and electrons, and so on. This is called “reductionism”. However, when faced with the actual nature, this idea had its limits, and when it was considered as a many-body system, a qualitatively different universality was found, giving rise to new trends in physics such as complex systems, chaos theory, probability theory, and condensed matter physics.
J Material: Physics of Strongly Correlated Systems
Electronic Properties of Solids
Electronic Properties of Low-dimensional Materials