En las fronteras de la Materia Condensada

Usually first order liquid-solid phase transitions imply a disorder-order structural transformation. Vortex matter in superconductors has been proved to be a very useful system to study phase transitions in condensed matter physics. This soft matter presents either first or second order phase transition depending on the characteristics of the samples. It is widely accepted that the first order vortex liquid-solid phase transition is associated with a crystalline solid phase and the second order transition with an amorphous one. The combination of a technique that determines the order of the transition with the visualization of the vortex structure has allowed the detection, for the first time, of a first order liquid-solid transition without structural symmetry change. The results show that the proposed correlation between the order of the transition and the topology of the solid phase is not a necessary condition. This opens an important question on the microscopic origin of liquid-solid phase transitions in vortex matter.