Event Details

Dissipation mechanisms in the integer Quantum Hall State

Dissipationless topologically protected states are of major fundamental interest as well as of practical importance to areas of metrology and quantum information technology. Although topological protection is theoretically robust, in realistic devices it is often fragile against various dissipative mechanisms, which are difficult to probe directly because of their microscopic origins. In this talk, I will discuss scanning nanothermometry measurements on ultra-large graphene mesas and the microscopic mechanisms undermining dissipationless transport in the Quantum Hall State. By simultaneous imaging both thermal and scanning gate signals, I will show that the dissipation in integer fillings is governed by ‘crosstalk’ between counterpropagating pairs of downstream and upstream channels at graphene boundaries. Instead of local Joule heating, however, the dissipation mechanism comprises two distinct and spatially separated processes. These findings offer a crucial insight into the mechanisms concealing the true topological protection and suggest venues for engineering more robust quantum states for device applications.