  Entanglement features of the ground state of disordered quantum matter are
often captured by an infinite randomness fixed point that, for a variety of
models, is the random singlet phase. Although a copious number of studies
covers bipartite entanglement in pure states, at present, less is known for
mixed states and tripartite settings. Our goal is to gain insights in this
direction by studying the negativity spectrum in the random singlet phase.
Through the strong disorder renormalization group technique, we derive analytic
formulas for the universal scaling of the disorder averaged moments of the
partially transposed reduced density matrix. Our analytic predictions are
checked against a numerical implementation of the strong disorder
renormalization group and against exact computations for the XX spin chain (a
model in which free fermion techniques apply). Importantly, our results show
that the negativity and logarithmic negativity are not trivially related after
the average over the disorder.
