Flux-flow resonant current steps in intrinsic Josephson junctions on Bi₂Sr₂CaCu₂O₈ single crystal

A mesa with a-b plane dimensions of 12 μm × 12 μm was patterned on Bi₂Sr₂CaCu₂O₈ single crystal, after which two separate electrical contacts were carefully fabricated on the top of the mesa to ensure a standard four-probe arrangement. With contact resistance excluded, the measured current-voltage (I-V) curves featured high voltage resolution. Voltage jumps up to 20 mV and remarkable hysteresis at 4.2 K indicated typical superconductor-insulator-superconductor properties. A few sharp current steps started to manifest themselves clearly when a magnetic field of about 10 kOe was applied parallel to the a-b plane. Carefully studied were the dependences of the current steps on the magnetic fields and the operating temperatures. We attributed the field-induced steps to the flux-flow resonances, and the multisteps implied different modes existing in the stacked intrinsic junctions. The voltage region at which the steps occurred was of the order of millivolts, indicating possible high-frequency applications at mm and sub-mm wavebands.