Superheavy dark matter and IceCube neutrino signals: Bounds on decaying dark matter

Superheavy dark matter may show its presence in high-energy neutrino signals detected on Earth. From the latest results of IceCube, we could set the strongest lower bound on the lifetime of dark matter beyond 100 TeV around ${10}^{28}\text{ }\text{ }s$. The excess around a PeV is noticed and may be interpreted as the first signal of dark matter even though further confirmation and dedicated searches are invited.