We demonstrate a geometrical effect on the depinning line (DL) of the flux line lattice of the Bi₂Sr₂CaCu₂O_8+δ high-T_c superconductor (HTSC) micrometer ring. The DL shifts to notably lower temperatures in comparison with bulk crystals and thin flakes of the same sample. The shift is attributed to a decrease in the overall pinning potential due to a double size effect, namely (a) the ring thickness \(\sim 1~\mu \)m being smaller than the pinning correlation length and (b) the increase in the effective London penetration depth of the vortices (Pearl vortices). The large shift of the DL to lower temperatures may influence the suitability of this HTSC for applications in microstrip antennas and THz emitters.

中文翻译：

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Bi 2 Sr 2 CaCu 2 O 8 +δ微米细环的磁化及其脱钉线

我们证明了Bi ₂ Sr ₂ CaCu ₂ O _{8+ δ}高T _c超导体（HTSC）微米环的通量线晶格的脱钉线（DL）的几何效应。与同一样品的块状晶体和薄片相比，DL的温度明显降低。该偏移归因于由于双重尺寸效应而导致的总钉扎电势的降低，即（a）环厚度\（\ sim 1〜\ mu \）m小于钉扎相关长度，并且（b）涡旋（Pearl涡旋）的有效伦敦穿透深度的增加。DL向较低温度的大偏移可能会影响该HTSC在微带天线和THz发射器中的适用性。