Transport signature of helical hinge states of quasi-one-dimensional topological insulators

Higher-order topological insulators exhibit protected corner or hinge states generalizing the bulk-boundary correspondence. The quasi-one-dimensional materials Bi₄Br₄ and Bi₄I₄ have been predicted to be prototypical examples of such topological matter with helical hinge states along the atomic chain direction. We examine the electronic behavior of their helical hinge states and predict unique signatures in transport experiment. We further show how these signatures depend on the applied electric and magnetic fields.