Investigation of critical current density of submicron intrinsic Josephson junctions ofBi2Sr2CaCu2O8 + δ at 30 K

Abstract

The Cooper pair tunneling in the intrinsic Josephson junctions (IJJs)can be affected by quantum phase fluctuations when the resistance of asubmicron stack is in the range of the quantum resistance. To observe thisquantum effect we have fabricated stacks of IJJs of various in-plane area from4 µm2 downto 0.16 µm2 inBi2Sr2CaCu2O8 + δ single-crystalwhiskers using a three-dimensional focused-ion-beam etching technique. For stacks of in-plane area lessthan 1 µm2 a strong suppression in critical current density (Jc) isnoticed in current–voltage characteristics at 30 K. The possible mechanisms in this suppression ofJc arediscussed and the data analysis points to the quantum phase fluctuations as the most likely mechanismof this effect. We have achieved quantum fluctuations at 30 K reported for the first time ever forBi2Sr2CaCu2O8 + δ (Bi-2212) single-crystal whiskers.