A model of interacting fermions in one dimension proposed by the Japanese physicist Sin-Itiro Tomonaga (1906–79) in 1950 and analysed further by the American physicist Joaquin Luttinger (1923–97) in 1963. A Luttinger liquid is a non-Fermi liquid and hence has different properties from, for example, the properties of electrons in ordinary metals. The electrons in one-dimensional chains of certain organic molecules form a Luttinger liquid.