Temperature dependence of transverse magnetic focusing in a high-mobility heterostructure

The temperature dependence of Transverse Magnetic Focusing (TMF) is investigated in a two-dimensional electron system in a high-mobility GaAs/AlGaAs heterostructure at low temperatures T (electron mean free path 81 $\mu$m at 4.2 K). Two TMF configurations are studied $—$ a regular in-line configuration with distance between the injector and collector of L = 7 $\mu$m, and a bent configuration with L = 5 $\mu$m horizontal and 2 $\mu$m vertical. In both configurations, the TMF amplitude (non-local resistance R$_f$) shows a monotonic decrease as T is increased from 4 K to 20 K. This decay is analyzed by fitting R$_f$ according to different scattering mechanisms. Limitation of R$_f$ by acoustic phonon scattering is ruled out because 1/T does not provide a good fit to the experimental data. In fact, we observe R$_f$ $\sim$ 1/T$^2$, indicating the dominance of inelastic electron-electron interactions in limiting R$_f$. The role of electron-electron interactions hints at the existence of a hydrodynamic transport regime in a particular temperature range. The hydrodynamic regime has recently received increasing attention. The finding suggests that TMF, usually considered a purely ballistic phenomenon, may present hydrodynamic aspects as well.