Resistively shunted intrinsic Josephson junctions and their high frequency responses at a 3 mm waveband

We propose a new method for fabricating resistively shunted intrinsic Josephson junctions (RS-IJJs). Two mesas, measuring 6 × 6μm2 and 100 × 100 μm2 respectively in the a-b plane, have been fabricated in a Bi2Sr2CaCu2O8+x single crystal with a SiO layer evaporated in-between as an insulator. A gold stripe was sputtered onto the insulator to connect the mesas, thus effectively shunting the smaller one. The current–voltage (I–V) curves of such RS-IJJs have shown the typical behaviour of a resistively shunted junction with greatly reduced hysteresis and voltage jump. Under microwave irradiation at a 3 mm waveband, we have registered three types of Shapiro steps: conventional, sub-harmonic and zero-crossing. In this rapid communication, we discuss the fabrication details, as well as the observations of the Shapiro steps.