Advanced Undergraduate Laboratory

Department of Physics

University of Toronto

HTC: High Tc Superconductors

In late 1986 and early 1987 a revolution in superconductor technology occurred with the discovery of materials which are superconducting at temperatures above the boiling point of liquid nitrogen. Students manufacture from basic ingredients their own superconductor and then investigate its physical properties.Georg Bednorz and Alex Müller won the Nobel Prize in Physics in 1987 for this discovery.

Write-Up in PDF Format or Microsoft Word Format (docx).

(The experiment is currently located in MP239. Last write-up revision: February 2018.)

Note: This experiment has an additional new kit set-up that uses premade samples for studies of both resistivity and magnetization is YBCO and BSSCO. The manual does not yet include information on these measurements; instructions will be provided by the supervising professor and the Colorado Superconductor manual below. Students doing the kit version of the experiment should still, however, carefully read the Introduction, Theory, and Safety sections of the HTC write-up.

Technical Resources:

• "A Method of Measuring Specific Resistivity and Hall Effect of Discs of Arbitrary Shape" by L. J. van der Pauw, Philips Research Reports 13, 1958 (2.8 MB)
• Specac Autotouch Hydraulic Press manual.
• thermocouple.py - A python module that converts thermocouple voltages into temperature, or vice versa, based on NIST thermocouple tables.
• KSL-1100X furnace manual
• Experiment Guide for Superconductor Demonstrations Version 7.0, Colorado Superconductor (2007).
• If you are not familiar with Lock-In amplifiers, please watch this video:

• If your sample is green, you have likely produced YBa₂Cu₃O₅ instead of the desired YBa₂Cu₃O_7-x
.

Physics Resources:

• Some papers on the temperature dependence of the resistivity of YBCO
  • "Analysis of Resistance Data on a Good Ceramic Sample of YBa₂Cu₃O_7-x " by David M. Eagles, Jpn. J. Appl. Phys. 32 (1993) pp. 1077-1081.
  • "YBCO samples as a possible thermoelectric material" by J. E. Rodriguez, Physica Status Solidi 2 (2005) 3605–3608.
  • "Thermal fluctuations near a phase transition probed through the electrical resistivity of high-temperature superconductors" by Noelia Cotón et al., American Journal of Physics (2010) 310-316.
• High-Temperature Superconductors from the CRC Handbook of Chemistry and Physics

3^rd year Engineering Science undergraduate, Xida Chen, with a High-Tc pellet that he made with his partner, Jasper Chan. The pellet was cooled to about 77K in a bath of liquid Nitrogen, then placed above the magnets. It is floating several millimeters above the surface of the magnets!.

Graph of sample resistance versus temperature for a YCBO sample created by 3^rd year Engineering Science undergraduates, Jasper Chan and Xida Chen.

Last updated on 8 October 2020