Images of edge current in InAs/GaSb quantum wells
  Quantum spin Hall devices with edges much longer than several microns do not display ballistic transport: that is, their measured conductances are much less than $e^2/h$ per edge. We imaged edge currents in InAs/GaSb quantum wells with long edges and determined an effective edge resistance. Surprisingly, although the effective edge resistance is much greater than $h/e^2$, it is independent of temperature up to 30 K within experimental resolution. Known candidate scattering mechanisms do not explain our observation of an effective edge resistance that is large yet temperature-independent. 
Eric M. Spanton, Katja C. Nowack, Lingjie Du, Gerard Sullivan, Rui-Rui   Du, and Kathryn A. Moler
cond-mat.mes-hall