Singularities in Hessian element distributions of amorphous media

Abstract

We show that the distribution of elements $H$ in the Hessian matrices associated with amorphous materials exhibit cusp singularities $P(H) \sim {\lvert H \rvert}^{\gamma}$ with an exponent $\gamma < 0$, as $\lvert H \rvert \to 0$. We exploit the rotational invariance of the underlying disorder in amorphous structures to derive these exponents exactly for systems interacting via radially symmetric potentials. We show that $\gamma$ depends only on the degree of smoothness $n$ of the potential of interaction between the constituent particles at the cut-off distance, independent of the details of interaction in both two and three dimensions. We verify our predictions with numerical simulations of models of structural glass formers. Finally, we show that such cusp singularities affect the stability of amorphous solids, through the distributions of the minimum eigenvalue of the Hessian matrix.