Ricard Alert

Inverting the landscape

 

Many everyday phenomena are known in Physics as first-order phase transitions, in which a substance changes its physical state. Examples of these are the boiling of water in a pan, where liquid water transforms into vapour, or the melting of an ice cube in a glass of whisky, where water goes from the solid to the liquid phase. In this paper, we discover a new scenario of first-order phase transitions. The equilibrium state of a substance is always that of minimum energy. If one imagines the energy of a system as the height of the relief of a mountain landscape, the equilibrium state would correspond to standing on the valley. A phase transition usually takes place when a nearby valley gets deeper and one can move to it. In our paper, we show that a first-order phase transition can also occur because of a complete inversion of the energy landscape, as if the mountains’ relief suddenly became that of its reflection on a lake. Theory, simulations, and experiments on a crystal of magnetic particles are used to demonstrate the non-conventional features of the so-called “landscape-inversion phase transition”, thus adding new ingredients to the traditional field of phase transitions.