%0 Journal Article %A Corps, Angel L. %A Molina, Rafael A. %A Relaño Pérez, Armando %T Thouless energy challenges thermalization on the ergodic side of the many-body localization transition %D 2020 %@ 2469-9950 %U https://hdl.handle.net/20.500.14352/6420 %X We study the ergodic side of the many-body localization transition in its standard model, the disordered Heisenberg quantum spin chain. We show that the Thouless energy, extracted from long-range spectral statistics and the power-spectrum of the full momentum distribution fluctuations, is not large enough to guarantee thermalization. We find that both estimates coincide and behave nonmonotonically, exhibiting a strong peak at an intermediate value of the disorder. Furthermore, we show that nonthermalizing initial conditions occur well within the ergodic phase with larger probability than expected. Finally, we propose a mechanism, driven by the Thouless energy and the presence of anomalous events, for the transition to the localized phase. %~