Strongly Coupled Electron Matter

Strongly coupled systems pose a distinct problem for theoretical physics. In such systems, the physics arises from collective organization rather than from a sum of the constituents. A classic problem of strong coupling is high-temperature superconductivity. Bardeen-Cooper-Schrieffer solved the problem of superconductivity in metals by appealing to a simple organizing principle of metals: all the physics of the normal state are controlled by the properties of free particles. A similar simplification cannot be made for the cuprate superconductors, as these systems are doped Mott insulators, a state of matter in which the electron interactions dominate. Precisely what to do in this intractable parameter space is the key problem facing theorists in the field. If a fixed point at strong coupling exists, then definitive progress can be made. Professor Phillips will use his Center appointment to pursue two projects which are central to the physics of strong electron correlation in copper-oxide superconductors: 1) a demonstration that the local Mott physics in the normal state of the cuprate superconductors is controlled by a non-trivial IR fixed point and 2) an exploration of superconductivity at such a fixed point. The second project will be solved by borrowing ideas from string theory in which the strong correlations will be replaced by an essentially free gravity problem. This synergy between concepts and tools developed first in high-energy physics and their eventual application to solid state systems is a distinct feature of Professor Phillips’s work.