David Thouless

David Thouless (1934–2019) was a British-American theoretical physicist whose work helped establish the theory of superconductivity, superfluidity, and topological phases of matter.

Kosterlitz–Thouless transition: A Berezinskii–Kosterlitz–Thouless transition driven by the binding or unbinding of topological defects in two dimensions. Thouless’s work with Michael Kosterlitz explained this transition and its unusual form of phase ordering.
Topological phase of matter: A phase distinguished by global topological properties of its quantum states rather than by conventional symmetry breaking. Thouless’s research helped establish this way of classifying matter.
Michael Kosterlitz: A British-American physicist whose work with David Thouless explained a topological phase transition in two dimensions. Their collaboration produced the theory now commonly called the Kosterlitz–Thouless transition.
University of Cambridge: A public research university in Cambridge, England, founded in 1209. Thouless studied physics there before pursuing research in the United States.
Berezinskii–Kosterlitz–Thouless transition: A phase transition in two-dimensional systems caused by the binding or unbinding of vortex–antivortex pairs. Thouless’s contributions helped establish this broader framework for transitions without conventional long-range order.
Chern number: An integer topological invariant that characterizes certain quantum states and governs quantized physical responses. Chern numbers provide a mathematical route to the quantized Hall conductance studied by Thouless.
F. Duncan Haldane: A British-born theoretical physicist whose work revealed topological phases in one-dimensional spin chains and quantum systems. Haldane shared the 2016 Nobel Prize with Thouless for discoveries about topological phases.
Harvard University: A private research university in Cambridge, Massachusetts, founded in 1636. Thouless completed his doctoral research at Harvard under Julian Schwinger.
Thouless pump: A quantized transport process in which a cyclic change of a one-dimensional system moves an integer number of particles. This phenomenon connects Thouless’s ideas about topology to measurable particle transport.
Topological invariant: A quantity unchanged by continuous deformations of a mathematical object or physical system. Topological invariants capture the robustness central to Thouless’s account of quantum Hall conductance.

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Duncan HaldaneRelated: Thouless’s theory of quantized conductance shaped the intellectual setting for Haldane’s work.