Landau Theory for Disorder-Driven Metal-Insulator Transitions

Disorder driven metal-insulator transitions have long defied proper understanding, despite representing one of the basic phenomena in solid state physics. Here we first provide a brief overview of key experimental features, providing guidance. We then present a new theoretical approach that makes it possible to formulate Landau-like order parameter theory at the saddle-point level, capturing most experimental puzzles. It also allows an investigation of systematic fluctuation corrections, suggesting a finite upper critical dimension, and a formulation of an appropriate Landau-Ginzburg description of spatial correlations currently studied by scanning probes.