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arXiv · 1911.01736

BKT transition observed in magnetic and electric properties of YBa$_2$Cu$_3$O$_{7-\delta}$ single crystals

V. I. Nizhankovskiy·K. Rogacki
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Abstract

Superconductivity of YBa$_2$Cu$_3$O$_{7-\delta}$ single crystals was investigated in small magnetic fields. In magnetic measurements the superconducting transition for $\textbf{H} \| c$ appears 0.4 K higher than for $\textbf{H} \bot c$. In this temperature range superconductivity is two-dimensional and the total thickness of superconducting layers is about 0.83 of the sample thickness, which is a consequence of the occurrence of the quasi-insulating plane in the unit cell of the crystal structure. Resistivity in the \textit{ab}-plane and along the \textit{c}-axis was measured simultaneously. In these measurements two-dimensional superconductivity was observed in a temperature range of 0.6-0.8 K with the clear signs of the Berezinskii-Kosterlitz-Touless (BKT) transition which occurs approximately 0.15 K below $T_c$, the mean-field transition temperature.

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V. I. Nizhankovskiy, K. Rogacki. 2019-11-05. BKT transition observed in magnetic and electric properties of YBa$_2$Cu$_3$O$_{7-\delta}$ single crystals. https://doi.org/10.1103/physrevb.100.104510

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