Quantum phase transitions

Abstract

These are notes for lectures delivered at the NATO ASI on Dynamics in Leiden, The Netherlands, in July 1998. The main concepts relating to quantum phase transitions are explained, using the paramagnet-to-ferromagnet transition of itinerant electrons as the primary example. Some aspects of metal-insulator transitions are also briefly discussed. The exposition is strictly pedagogical in nature, with no ambitions with respect to completeness or going into technical details. The goal of the lectures is to provide a bridge between textbooks on classical critical phenomena and the current literature on quantum phase transitions. Some familiarity with the concepts of classical phase transitions is helpful, but not absolutely necessary.