Questionable stability of dissipative topological models for classical and quantum systems
(PHYSorg.com Physics)

Energy conservation lies at the core of every physical theory. Effective mathematical models however can feature energy gain and/or loss and thus break the energy conservation law by only capturing the physics of a subsystem. As a result, the Hamiltonian, the function that describes the system`s energy, loses an important mathematical property: it is no longer Hermitian. Such non-Hermitian Hamiltonians have successfully described experimental setups for both classical problems-in e.g. some optical systems and electrical circuits-and quantum ones, in modelling the motion of electrons in crystalline solids. In a new paper in EPJ D, physicists Rebekka Koch from the University of Amsterdam in the Netherlands and Jan Carl Budich from Technische Universität Dresden, in Germany, describe how these functions provide new insights into behaviour at the edges of topological materials.