Periodic Peak Modulations in Bi-2212 Stacks Coupled to a Submicrometer Hole

S.-J Kim

doi:10.1109/tasc.2009.2018193

Abstract

Coupled stacked Josephson junctions (SJJs) in high-T c superconducting (HTS) Bi 2 Sr 2 CaCu 2 O 8+d (Bi-2212) are fabricated with a refined coupling configuration of a hole. Two types of coupled SJJs with a completely perforated hole of 0.1 mum x 0.2 mum and 0.2 mum x 0.4 mum were fabricated by using a 3-D focused ion beam (FIB) etching method. Those SJJs exhibited clearly oscillated critical current I c under external magnetic fields H e . With applying H e , the clear periodic modulation patterns of I c are obtained and well fitted to the calculated value from the hole area of 0.02 mum 2 , DeltaB(= Phi 0 /S) , where S is hole area. The width and uniform transport properties of SJJs are confirmed by flux flow resistance R ff -H e measurement with a bias current I b of 1 muA at 10 K. We also investigated external field angle thetas i dependence of junction resistance R j at 1 T and 10 K. When a constant H e of 1 T and a I b of 1 muA are applied to the sample with changing thetas i , unspecified equidistant and periodic peak structures in SJJs were induced. Those peaks dependence on thetas i under H e were experimentally observed by measurement of the R j . We assign the origin of the peaks to the interrelations between the periodic mechanical vibrations of sample stage and the quantized flux behaviors around a submicrometer hole. Those peak structures of I c and R j could be excited by H e ,thetas i ,I b , and some external signals from the peculiar properties of SJJs coupled to a hole.

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