Spreading dynamics in the Hatano-Nelson model with disorder

The non-Hermitian skin effect is the accumulation of eigenstates at the boundaries, reflecting the system's nonreciprocity. Introducing disorder leads to a competition between the skin effect and Anderson localization, giving rise to the skin-Anderson transition. Here, we investigate wave packet spreading in the disordered Hatano-Nelson model and uncover distinct dynamical behaviors across different regimes. In the clean limit, transport is unidirectionally ballistic ({\Delta}x ~ t) due to nonreciprocity. For weak disorder, where skin and Anderson-localized modes coexist, transport transitions from ballistic at early times to superdiffusive ({\Delta}x ~ t^{2/3}) at long times. In the deeply Anderson-localized regime, initial diffusion ({\Delta}x ~ t^{1/2}) eventually gives way to superdiffusive spreading. We examine how these scaling behaviors emerge from the system's spectral properties and eigenstate localization behaviors. Our work unveils the rich dynamics driven by nonreciprocity and disorder in non-Hermitian systems.