Quantum Phase Transitions in Condensed Matter and Atomic Physics

Harvard University, Cambridge MA

Investigators

Abstract

This grant supports theoretical research on fundamental condensed matter physics based on the study of quantum phase transitions. Also included are studies of the connections between atomic physics and condensed matter physics; in particular studies of systems of trapped ultracold atoms. Quantum phase transitions are changes in state of matter at the absolute zero of temperature, driven by changes in a tuning parameter such as carrier concentration, magnetic field strength, or pressure. Studies of materials at low temperatures in the vicinity of quantum critical points between conventional phases have proven to be fertile ground for finding new quantum phases with novel physical properties. A number of studies will be undertaken of intermetallic compounds and trapped atomic gases analyzing some of the many quantum phases and transitions that have become accessible by recent advances in experimental technologies. For the cuprate superconductors, extensions of the PI's recent theory for the superfluid-insulator transition in the vicinity of 1/8 carrier doping will be made, to allow specific predictions for high precision scanning tunneling microscopy and neutron scattering experiments. A central ingredient of the theory is the novel role played by the vortices of the superconductor, which behave like quantum particles moving in a magnetic field. Also to be studied is the interplay between the density wave order of the proximate Mott insulator and the nodal quasiparticles with the aim of obtaining predictions for thermal transport experiments. Also to be studied are magnetic phase transitions in the intermetallic heavy fermion compounds, exploring the emergence of deconfined fractionalized excitations at the quantum critical point. For the trapped ultracold atomic systems, new quantum critical points have been described that can be explored experimentally on optical lattices and near a Feshbach resonance. Detailed theories of these experiments will be developed. The PI has written a seminal and widely used textbook, Quantum Phase Transitions, that is in its second printing as a paperback. The PI is working on a second edition that will incorporate ideas from this research, and adding sections to enable wider accessibility. The PI has also presented lectures and written articles on this research for a wide variety of audiences. This will continue. Students at all levels will be involved with this research. %%% This project involves theoretical studies of condensed matter physics and its connections to atomic physics. The project is based on quantum phase transitions. These are phase transitions (think of water turning to ice) that occur at absolute zero of temperature where quantum effects dominate. These phase transitions often lead to new and novel states of matter. These studies are part of the fundamental core area of modern condensed matter physics, and yet may someday find technological applications. The PI has written a seminal and widely used textbook, Quantum Phase Transitions, that is in its second printing as a paperback. The PI is working on a second edition that will incorporate ideas from this research, and adding sections to enable wider accessibility. The PI has also presented lectures and written articles on this research for a wide variety of audiences. This will continue. Students at all levels will be involved with this research. ***