'Inverse' melting of a vortex lattice

Citation
N. Avraham et al., 'Inverse' melting of a vortex lattice, NATURE, 411(6836), 2001, pp. 451-454
Citations number
30
Categorie Soggetti
Multidisciplinary,Multidisciplinary,Multidisciplinary
Journal title
NATURE
ISSN journal
00280836 → ACNP
Volume
411
Issue
6836
Year of publication
2001
Pages
451 - 454
Database
ISI
SICI code
0028-0836(20010524)411:6836<451:'MOAVL>2.0.ZU;2-M
Abstract
Inverse melting is the process in which a crystal reversibly transforms int o a liquid or amorphous phase when its temperature is decreased. Such a pro cess is considered to be very rare(1), and the search for it is often hampe red by the formation of non-equilibrium states or intermediate phases(2). H ere we report the discovery of first-order inverse melting of the lattice f ormed by magnetic flux lines in a high-temperature superconductor. At low t emperatures, disorder in the material pins the vortices, preventing the obs ervation 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 lat tice into a disordered vortex phase as the temperature is decreased. The or dered lattice has larger entropy than the low-temperature disordered phase. The mechanism of the first-order phase transition changes gradually from t hermally induced melting at high temperatures to a disorder-induced transit ion at low temperatures.