The Superconductivity Lab
Building: K.B. Weissman
Magnetic Vortices in High Temperature SuperconductorsThe magnetic field penetrates into superconductors in a form of quantum flux lines or vortices, which can be regarded as particles. The vortices establish a unique vortex matter that provides a remarkable example of condensed state with tunable parameters. The density of the constituent particles (vortices) and their interactions can be changed over several orders of magnitude in a controllable way, simply by varying the external magnetic field. As a result, the vortex matter displays a rich phase diagram that includes several vortex solid, liquid, and gaseous phases, the exact nature of which is still unclear.
The vortex matter phase diagram and the dynamics of vortices in high-temperature superconductors are being investigated by novel experimental techniques including microscopic arrays of Hall sensors and magneto-optical imaging. In addition, transport and other complementary methods are used for investigation of high-temperature as well as conventional superconductor single crystals.
The sensors are fabricated using GaAs/AlGaAs two-dimensional electrongas heterostructures, which provide very sensitive measurement of the local magnetic field and, hence, the local density of vortices across the sample. Using this technique, several new phenomena were revealed, including the first-order vortex-lattice melting or sublimation transition, the geometrical barrier effect, the disorder driven solid-solid phase transition at low temperatures, and the dominant role of the surface barriers. The magneto-optical system with cooled digital CCD camera is used for direct imaging and investigation of vortex dynamics and phase transitions.
Link to our Superconductivity Lab.
E. Zeldov, D. Majer, M. Konczykowski, V. B. Geshkenbein, V. M. Vinokur, and H. Shtrikman, "Thermodynamic Observation of First-Order Vortex-Lattice Melting Transition in Bi2Sr2CaCu2O8", Nature 375, pp. 373-376 (1995).
D. T. Fuchs, E. Zeldov, T. Tamegai, S. Ooi, M. Rappaport, and H. Shtrikman, "Possible New Vortex Matter Phases in Bi2Sr2CaCu2O8", Phys. Rev. Lett. 80, pp. 4971-4974 (1998).
D. T. Fuchs, E. Zeldov, M. Rappaport, T. Tamegai, S. Ooi, and H. Shtrikman, "Transport Properties Governed by Surface Barriers in Bi2Sr2CaCu2O8", Nature 391, pp. 373-376 (1998).
Complete List of References