  Quantum spin Hall insulators are characterized by topologically protected
counterpropagating edge states. Here we study the dynamical response of these
helical edge states under a time-dependent flux biasing, in the presence of a
heat bath. It is shown that the relaxation time of the edge carriers can be
determined from a measurement of the dissipative response of topological
insulator disks. The effects of various perturbations, including Zeeman
coupling and disorder, are also discussed.
