研究目的
To experimentally study new characteristics of the SQUID-SI structure that yield further information about its current states under the integrated action of direct and alternating transport currents, as well as static and alternating magnetic fields.
研究成果
The study expanded the understanding of possible quantum states of the SQUID-SI structure and established methods for managing critical direct current (Ic) of the SQUID using alternating transport current and alternating current generated by an external alternating magnetic field. A new type of discrete stationary state was discovered during the transition of the interferometer to the resistive state, highlighting the potential for further research into postcritical quantum states of the structure.
研究不足
The study is limited to the effects observed at frequencies in the range of 20–75 Hz and does not explore higher frequencies. Additionally, the exact mechanisms behind the appearance and disappearance of current steps with increasing alternating current require further investigation.
1：Experimental Design and Method Selection:
The study involves the use of a superconducting quantum interference device (SQUID) shunted by a larger superconducting inductance (SI). The methodology includes passing alternating transport current through the structure and applying an external alternating magnetic field simultaneously with a direct transport current to observe changes in the critical current and discrete current states.
2：Sample Selection and Data Sources:
The SQUID-SI structure is a cylindrical coil made of superconducting niobium microwire with a diameter of 70 μm, forming a pressure point contact. The structure is placed in liquid helium at normal pressure (T = 4.2 K).
3：2 K).
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: The setup includes a fluxgate magnetometer sensor for measuring the magnetic field in the coil, a voltage source for generating current, a sound generator for alternating current, and a two-coordinate electromechanical recorder for recording the current characteristics.
4：Experimental Procedures and Operational Workflow:
The experiment involves measuring the dependencies of current I1 in inductance L on transport current I at different values of current IH excited by the external magnetic field H, and observing the effects of alternating transport current I～ on the structure.
5：Data Analysis Methods:
The analysis includes determining the critical current of the SQUID and observing the periodic steps in the dependency I1(I), which are the result of periodic changes in the quantum current states of an asymmetric SQUID.
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