This experiment is an introduction to various fundamental concepts of superconductivity.
Students will cool down a superconductor—either a high-temperature superconductor or a conventional (“normal”) superconductor—below its critical temperature and record the resistance using a four-point measurement. By applying a current through the superconductor, the critical current will be determined.
The second part of the practical focuses on the Meissner–Ochsenfeld effect in high-(T_c) type-II superconductors, the emergence of the vortex state, and flux pinning. Students cycle a superconductor through its superconducting and non-superconducting states in various external magnetic fields.
This demonstrates the implications of flux pinning and the Meissner–Ochsenfeld effect using the example of a levitating superconductor.
This experiment introduces students to the concept of magnetic susceptibility and measures its value across a superconducting transition.
The experiment is based on an A.C. mutual inductance technique. An alternating magnetic field is applied through an excitation coil, and the induced response is detected using a pair of oppositely connected pick-up coils. When a superconducting sample is placed in one of the pick-up coils, its strong diamagnetic response, arising from the Meissner effect, produces a measurable change in the induced voltage.
Students will study the temperature dependence of this response and identify the transition into the superconducting state. The experiment teaches important concepts of magnetization, magnetic shielding, complex susceptibility, and provides exposure to sensitive detection techniques.
Phase-sensitive detection is a powerful technique for extracting signals at a specific frequency while suppressing broadband background noise.
This experiment provides an introduction to the lock-in amplifier, a fundamental instrument for many modern experimental techniques. Participants will design and construct a lock-in circuit from basic components, exploring its internal architecture and operational constraints.
The lab bridges the gap between the mathematical model and its physical implementation, allowing students to gain an intuitive understanding of the inner workings of this device.