Fig. 1: Schematic illustration of the measurement at zero temperature.
From: Fundamental dissipation due to bound fermions in the zero-temperature limit
(Centre) The crossbar of the wire is moved in two phases along direction labelled x. All ramps begin by accelerating the wire from zero to a constant velocity (here v = 40 mm s−1, gray line) and then back to zero. The magnitude of the resulting flow field, vfl, in the coordinate system of the wire is shown with contour lines in the inset. The ramp is then either repeated in the same direction (up ramp, blue line) or in the opposite direction (down ramp, red line). Bound-state dynamics are probed by varying the waiting time Δt between the two phases. a The flow shifts both the bound-state energy spectrum, E(p), and the available bulk states as explained in the main text. After the acceleration, the population of bound quasiparticles (red circles) and quasiholes (blue circles) on the wire surface reaches a steady-state (point a along the wire trajectory). The schematic dispersion curves (black dash line at the surface, blue dash line in bulk) are drawn for the top (or bottom) generatrices of the wire, where the flow velocity is maximal. b During Δt, momentum exchange with the wire surface allows the exchange of bound quasiparticle populations between the branches (τ1). Within a branch, the population relaxes with τ2. c During an up ramp, if Δt ≲ τ1, the population imbalance results in less dissipation from quasiparticles escaping to bulk as compared with the first phase of motion. d In a down ramp, if Δt ≲ τ1, the dissipation will be enhanced. Note that the bound-state dispersion depends on surface specularity, and the Dirac dispersion illustrated here is chosen for simplicity.
