Single doublons as ergodic bubbles

We illustrate a remarkably simple mechanism in which single doublon excitations trigger the generation of ergodic bubbles, which thermalize extensive localized systems. We provide analytical estimates showing how the critical disorder strength for such mechanism depends on singlon densities, which are nicely supported by numerical exact-diagonalization simulations. Our predictions equally apply to fermionic and bosonic systems and are definitively accessible by ongoing experiments simulating synthetic quantum lattices.