Photothermal imaging of high T(sub c) superconductor
Abstract
The thermal conductivities of the new high-T sub c superconductors show marked changes with temperature, as does their electrical conductivity. As the temperature is lowered, the thermal conductivity abruptly rises near T sub c. Measurements made along the copper-oxide planes of single-crystal bismuth compounds show jumps as large as 70 percent. Since the thermal conductivity in these materials is dominated by lattice conduction, this behavior clearly demonstrates a coupling between the electrical carriers and phonons. The rise at T sub c is likely due to a reduction in phonon scattering as electrons become superconducting pairs. To date, these types of measurements have been made on amorphous samples and along the copper-oxide, or conducting, planes of single-crystal materials. Measurements are hampered by the difficulty of getting appropriately sized samples; the dimensions of single crystallites tend to be small and frequently the samples are oddly shaped. We demonstrate a simple technique for making point measurements of thermal conductivity in these materials. The technique is nondestructive, has sub-micron resolution, and can measure the conductivity in a specified direction. The goal is to make a more complete measurement of the behavior of thermal conductivity near T sub c, including measurements both along the c-axis, and along the Cu-O planes.
- Publication:
-
Presented at the Institute of Electrical and Electronic Engineering Ultrasonics Symposium
- Pub Date:
- September 1988
- Bibcode:
- 1988ieee.symp....2F
- Keywords:
-
- Barium Compounds;
- Imaging Techniques;
- Superconductors;
- Thermal Conductivity;
- Yttrium Compounds;
- Copper Oxides;
- Low Temperature;
- Polycrystals;
- Single Crystals;
- Solid-State Physics