Superconductivity

About the experiment

Superconducting phenomena are among the most fascinating features in physics, and the Josephson effect is the most interesting of all. In 1962, Brian Josephson predicted that electron pairs could tunnel without resistance through an insulating barrier between two superconductors. A DC current can flow through the junction with no potential difference; but when a DC voltage is applied together with a small alternating voltage, the current-voltage curve shows a characteristic step structure. From this step structure the value of 2e/h can be calculated easily and accurately, an exciting consequence of the properties of the junction. The ratio e/h appears throughout atomic and condensed matter physics. In this experiment you will learn some vacuum-evaporation and low-temperature techniques which are used in many research laboratories. You will fabricate your own SIN (superconductor-insulator-normal metal) and SIS (superconductor-insulator-superconductor) tunnel junctions in a vacuum evaporator, dip them into liquid helium and measure their voltage-current characteristics. The SIS junctions exhibit the famous Josephson Effect, whereby an electrical current flows across the junction without any voltage drop. When you make a circuit with 2 such junctions, you get a "SQUID", i.e. a Superconducting Quantum Interference Device.

What you will learn

Vacuum techniques and thin film deposition
Experience with liquid helium and cryo
Introduction to superconductivity
Introduction to the Josephson Effect

Preparation

Review cryo safety and discuss with instructor.

Required reading:

Supplementary materials

Instruments:

Vidoes:

Superconductor Experiment - Meissner Effect