Graviton-like excitation observed with predicted chirality in fractional quantum Hall liquids

Fractional quantum Hall liquids are the prototypical topological states of matter, whose universal topological properties are well understood in most cases (with few exceptions that will be discussed later). However, as emphasized by Duncan Haldane, who shared the 2016 Nobel Prize for his contribution to topological physics in condensed matter, purely topological descriptions of fractional quantum Hall liquids are incomplete because they overlook a geometrical aspect of the physics. Based on this insight, Haldane and his Princeton associates1 argued that the long-wavelength collective excitations of fractional quantum Hall liquids correspond to oscillation of this geometry.