Deconfined Quantum Critical Points

TLDR

Second‑order phase transitions, foundational to statistical mechanics, are governed by an observable order parameter whose long‑distance fluctuations are described by a continuum field theory. The authors aim to show that quantum interference near second‑order quantum phase transitions invalidates the conventional paradigm and to propose a theory of deconfined quantum critical points in two‑dimensional antiferromagnets that could resolve experimental puzzles in correlated electron systems. Their theory describes critical points separating confining phases, where quantum interference generates emergent gauge fields and deconfined fractionalized excitations. The critical theory reveals emergent gauge fields and deconfined fractionalized excitations, suggesting that this paradigm could resolve experimental puzzles in correlated electron systems.

Abstract

The theory of second-order phase transitions is one of the foundations of modern statistical mechanics and condensed-matter theory. A central concept is the observable order parameter, whose nonzero average value characterizes one or more phases. At large distances and long times, fluctuations of the order parameter(s) are described by a continuum field theory, and these dominate the physics near such phase transitions. We show that near second-order quantum phase transitions, subtle quantum interference effects can invalidate this paradigm, and we present a theory of quantum critical points in a variety of experimentally relevant two-dimensional antiferromagnets. The critical points separate phases characterized by conventional “confining” order parameters. Nevertheless, the critical theory contains an emergent gauge field and “deconfined” degrees of freedom associated with fractionalization of the order parameters. We propose that this paradigm for quantum criticality may be the key to resolving a number of experimental puzzles in correlated electron systems and offer a new perspective on the properties of complex materials.