Presenation by A.J. Millis on "Disentangling Electronic and Lattice Contributions to Corelated Electron Phenomena."

Many collective electronic phenomena, including  ``Mott’’ metal-insulator transition, the excitonic insulator, and nematic (rotational symmetry breaking) states involve both an electronic order parameter and a change in ionic positions, and the relative importance of electronic and lattice effects has been for many years the subject of controversy.  This talk will present a theoretical framework that enables a sharp formulation of the question and a calculational schema that in many cases enables resolution of this controversy, showing in particular that in several materials that had been believed to exhibit electronically driven transitions  the lattice in fact plays a crucial role.