‘Fragile Superconductivity’: A Kinetic Glass Transition in the Vortex Matter of the High-temperature Superconductor YBa2 Cu3O7-δ

Abstract

Using high-resolution thermal expansion and magnetization measurements, we provide experimental evidence for a kinetic glass transition in the vortex matter of YBa 2 Cu 3 O 7-δ with some disorder. This transition, which represents the true superconducting transition in a magnetic field, exhibits many of the features of the usual glass transition found in supercooled structural liquids such as window glass. We demonstrate, using both kinetic and thermodynamic criteria, that this vortex matter is the most fragile system known to date, which we argue makes it possible to investigate the behavior very close to the Kauzmann temperature. Vortex matter, we suggest, may be a model system to study glassy behavior in general, which is expected to lead to a better understanding of the strong-fragile behavior in structural glasses.

Thermodynamic observation of a vortex melting transition in the Fe-based superconductor Ba0.5K0.5FeMak1, Philipp2, Cevey3 et al. 2013Phys. Rev. B167170View full textAdd to dashboardCite

“…1). Similar peaks have been observed at the vortex melting transition of YBa 2 Cu 3 O 7-δ [50] in samples with weak but finite flux pinning, which were attributed to the decay of some non-equilibrium screening currents near a second-order vortex melting transition [9]. Due to the close similarity of the present effects observed in the thermal expansion with those in YBCO, we also attribute these to an underlying vortex melting transition.…”

Vortex-lattice melting and paramagnetic depairing in the nematic superconductor FeSe

“…Upon heating, the pinning force, which couples the crystal lattice to the applied magnetic field, suddenly vanishes at the melting temperature, resulting in a prominent thermal-expansion anomaly. These types of anomaly in the cuprates were found to exhibit a behavior comparable to a kinetic glass transition and are most likely related to some glassy vortex phase [41,77], whose phase line, however, corresponds rather well to the first-order melting line in fully reversible crystals.…”

“…Prominent examples are κ-(BEDT-TTF) 2 Cu(NCS) 2 [36] and CeCoIn 5 [37,38], which exhibit thermodynamic evidence of a modulated phase having Cooper pairs with nonzero total momentum and a spatially nonuniform order parameter (r) [39,40]. While for the former the high-field phase appears to be a physical realization of the original Fulde-Ferrell-Larkin-Ovchinnikov state (FFLO) [41,42], the modulated phase in CeCoIn 5 is believed to result from a particular coupling between d-wave superconductivity and a field-induced incommensurate spin-density wave [43][44][45].…”

“…Similar irreversible peaks were already observed at the melting transition of both YBa 2 Cu 3 O 7−δ [75] and Ba 0.5 K 0.5 Fe 2 As 2 [30] crystals with weak flux pinning. Lortz et al [30,41] argued that they are due to the pinning force, which prohibits flux expulsion on cooling, thereby creating nonequilibrium flux gradients and concomitant shielding currents. Upon heating, the pinning force, which couples the crystal lattice to the applied magnetic field, suddenly vanishes at the melting temperature, resulting in a prominent thermal-expansion anomaly.…”

Magnetic torque evidence for the Fulde-Ferrell-Larkin-Ovchinnikov state in the layered organic superconductorκ−(BEDT−TTF)2CuBergk1, Demuer2, Sheikin3 et al. 2011Phys. Rev. B10481170View full textAdd to dashboardCite

“…Finally, in the measurement obtained at 1.8 • , the transition is completely "undercooled" toward a vortex-glass transition. 29,30 The vortex density is increasing rapidly with increasing angle which makes flux pinning effects and vortex-vortex interactions more effective. The time scale imposed by our magnetic-field sweep rate becomes too short for vortices to relax into the crystalline ground state at this angle.…”