Title: Direct measurement of superdiffusive and subdiffusive energy transport in disordered granular chains,
Abstract: The study of energy transport properties in heterogeneous materials has
attracted scientific interest for more than a century, and it continues to
offer fundamental and rich questions. One of the unanswered challenges is to
extend Anderson theory for uncorrelated and fully disordered lattices in
condensed-matter systems to physical settings in which additional effects
compete with disorder. Specifically, the effect of strong nonlinearity has been
largely unexplored experimentally, partly due to the paucity of testbeds that
can combine the effect of disorder and nonlinearity in a controllable manner.
Here we present the first systematic experimental study of energy transport and
localization properties in simultaneously disordered and nonlinear granular
crystals. We demonstrate experimentally that disorder and nonlinearity ---
which are known from decades of studies to individually favor energy
localization --- can in some sense "cancel each other out", resulting in the
destruction of wave localization. We also report that the combined effect of
disorder and nonlinearity can enable the manipulation of energy transport speed
in granular crystals from subdiffusive to superdiffusive ranges.