MIT News  August 19, 2021 Experimental realization of many-body localization (MBL) in solid-state systems has remained challenging. A team of researchers in the US (MIT, Argonne National Laboratory, Brookhaven National Laboratory, University of Wisconsin, Oak Ridge National Laboratory, UC Santa Barbara, University of Pennsylvania) reports evidence of a possible phonon MBL phase in disordered GaAs/AlAs superlattices. Through grazing-incidence inelastic X-ray scattering, they observed a strong deviation of the phonon population from equilibrium in samples doped with ErAs nanodots at low temperature, signaling a departure from thermalization. This behavior occurs within finite phonon energy and wavevector windows, suggesting a localization-thermalization crossover. […]