David Thouless

University of Washington

David James Thouless was a British–American theoretical physicist at the University of Washington, renowned for his profound contributions to condensed matter physics. He pioneered the mathematical description of topological phase transitions — changes of state in quantum matter that cannot be characterized by conventional symmetry-breaking. Together with J. Michael Kosterlitz, he described the Kosterlitz–Thouless transition in two-dimensional systems, showing how vortices drive a phase transition in thin superconducting films and magnets. Thouless also introduced the TKNN invariant (Thouless–Kohmoto–Nightingale–den Nijs), a topological integer that predicts quantized Hall conductance in quantum Hall systems. His theoretical framework laid the foundation for topological insulators and topological quantum computing, research directions that today drive major semiconductor R&D programs. Thouless shared the 2016 Nobel Prize in Physics with Haldane and Kosterlitz for these discoveries. His work underpins the physics of many modern electronic materials and represents a fundamental advance in our understanding of quantum matter.