'Inverse' melting of a vortex lattice

Article

关键词: HIGH-TEMPERATURE SUPERCONDUCTORS;    SINGLE-CRYSTALS;    BI2SR2CACU2O8 CRYSTALS;    PHASE-DIAGRAM;    TRANSITION;    YBA2CU3O7-DELTA;    GLASS;    IRREVERSIBILITY;    VORTICES;    BARRIERS;   

DOI  :  10.1038/35078021

来源: SCIE

【 摘 要 】

Inverse melting is the process in which a crystal reversibly transforms into a liquid or amorphous phase when its temperature is decreased. Such a process is considered to be very rare(1), and the search for it is often hampered by the formation of non-equilibrium states or intermediate phases(2). Here we report the discovery of first-order inverse melting of the lattice formed by magnetic flux lines in a high-temperature superconductor. At low temperatures, disorder in the material pins the vortices, preventing the observation of their equilibrium properties and therefore the determination of whether a phase transition occurs. But by using a technique(3) to 'dither' the vortices, we were able to equilibrate the lattice, which enabled us to obtain direct thermodynamic evidence of inverse melting of the ordered lattice into a disordered vortex phase as the temperature is decreased. The ordered lattice has larger entropy than the low-temperature disordered phase. The mechanism of the first-order phase transition changes gradually from thermally induced melting at high temperatures to a disorder-induced transition at low temperatures.

【 授权许可】

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