Getting hotter by heating less: How driven granular materials dissipate energy in excess

We investigate how the kinetic energy acquired by a dense granular system driven an external vibration depends on input energy. Our focus is dependence of behavior two main parameters: frequency and amplitude. find that there exists optimal forcing frequency, at which reaches maximal energy: if increased beyond such threshold, dissipates more recovers colder viscous state. Quite surprisingly, nonmonotonic found for amplitudes are sufficiently small to keep always in contact with driving oscillating plate. Studying dissipative properties system, we unveil striking difference between this standard resonance mechanism. This feature also observed microscopic scale single-grain dynamics can be interpreted as instance negative specific heat. An analytically solvable model based generalized forced-damped oscillator well reproduces phenomenology, illustrating role competing effects dissipation.