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Zeldov Study of the Vortex Matter Equilibrium BT Phase Diagram in Bi 2 Sr 2 CaCu 2 O 8 תאמ ףפוקנדייב םייח
| Content Provider | Semantic Scholar |
|---|---|
| Author | Zeldov, E. |
| Copyright Year | 2009 |
| Abstract | We studied the B-T phase diagram of the vortex matter in the layered high temperature superconductor Bi2Sr2CaCu2O8 using local magnetization measurements with micro Hall sensor arrays. At low temperatures we utilized the ‘shaking’ method, at which an in-plane ac field is applied to relax the vortex matter to its equilibrium state. Local dc magnetization measurements were taken along both field and temperature sweeps. We further probed the low temperature behavior of the vortices by combining the ac susceptibility technique together with the shaking method. We found, that in addition to equilibrating the vortex matter the shaking method results also in an artificial broadening of the thermodynamic features. Nevertheless, the first order melting transition was mapped with the dc measurement under equilibrium conditions down to below 30 K along both field and temperature sweeps, which showed excellent agreement. The temperature sweeps resulted in particularly sharp melting steps. The melting behavior changed its character from thermally induced at elevated temperatures, to disorder-driven inverse melting behavior at lower temperatures. The entropy difference per vortex at melting, well fitted by an increasing linear behavior, changes sign with the change in slope of the melting curve. Incorporating the shaking method with the ac susceptibility technique recovered an equilibrium melting behavior throughout the thermally induced part of the transition down to about 40 K, below which it was replaced with a dynamic feature. Both followed closely the previously mapped melting curve. We further mapped the first-order melting behavior in four samples with various oxygen doping levels, ranging between optimally and highly over-doped. The melting behavior indicated both a reduced anisotropy and enhanced pinning with increasing oxygen content. Overall, a more pronounced inverse melting behavior was mapped in the over-doped samples. Preliminary results indicate on a novel phase transition, possibly of second-order. It was detected by temperature sweeps, and showed weak field dependence both above and below the first-order melting line, crossing it in close proximity to its maximum. This suggests that the B-T phase diagram of the vortex matter in Bi2Sr2CaCu2O8 actually consists of four distinct phases. Their possible nature is discussed. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.weizmann.ac.il/condmat/superc/sites/condmat.superc/files/uploads/11.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
