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

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.