  We present magneto-transport study in an InAs/GaSb double quantum well
structure in the weak localization regime. As the charge carriers are depleted
using a top gate electrode, we observe a crossover from weak anti-localization
(WAL) to weak localization (WL), when the inelastic phase breaking time
decreases below spin-orbit characteristic time as a result of enhanced
electron-electron interactions at lower carrier concentrations. The same
crossover is observed with increasing temperature. The linear temperature
behavior of inelastic scattering rate indicates that the dominant phase
breaking mechanism in our 2D system is due to electron-electron interaction.
