Dirac Medallists 2018

The 2018 Dirac Medal and prize is awarded to professors: Subir Sachdev (Harvard University), Dam Thanh Son (University of Chicago) and Xiao-Gang Wen (Massachusetts Institute of Technology) for their independent contributions towards understanding novel phases in strongly interacting many-body systems, introducing original transdisciplinary techniques.

Subir Sachdev has made pioneering contributions to many areas of theoretical condensed matter physics. Of particular importance were the development of the theory of quantum critical phenomena in insulators, superconductors and metals; the theory of spin-liquid states of quantum antiferromagnets and the theory of fractionalized phases of matter; the study of novel deconfinement phase transitions; the theory of quantum matter without quasiparticles; and the application of many of these ideas to a priori unrelated problems in black hole physics, including a concrete model of non-Fermi liquids.
Dam Thanh Son was the first to understand that gauge/gravity duality could be used to address basic questions in strongly interacting many-body problems from cold trapped atoms to the quark-gluon plasma. He was able to show that one could compute transport coefficients, such as viscosity and conductivity, analytically in these systems, and that strong coupling typically gives rise to a bound on these coefficients. More recently, he has argued for the emergence of a Dirac fermion at the half-filled Landau level, work which has stimulated rapid developments in our understanding of three-dimensional gauge theories.

Xiao-Gang Wen has pioneered the concept of topological order as a new principle to understand gapped quantum systems. He found that states with topological order contain non-trivial boundary excitations, and he developed chiral Luttinger theory for the boundary states of quantum Hall systems. He realized that quantum Hall states fall outside of the usual Landau paradigm for characterizing phases of matter, and he showed how to classify them.  He unveiled deep connections between topological order and entanglement. More recently, he has developed the concept of symmetry protected topological phases. These ideas have close connections to anomalies in quantum field theory.