1. Superconductivity Michael Spreitzer

2. Overview „Superconductivity“ ? Who discovered it ? Meissner & Ochsenknecht effect? BCS – Theory Different types of superconductivity Applications

3. Superconductivity Zero resistance Expulsion of magnetic field lines

4. Critical temperature MaterialTcTc Gallium1.1K Aluminum1.2 K Indium3.4 K Tin3.7 K Mercury4.2 K Lead7.2 K Niobium9.3 K La-Ba-Cu-oxide17.9 K Y-Ba-Cu-oxide92 K Tl-Ba-Cu-oxide125 K Electrical resistance drops to zero Materals with a ct arround 120 K can be cooled down with liquid nitrogen (77K )

5. Heike Kamerlingh Onnes 1853-1926 Dutch physicist Liquified He 1908 (4K) 1911

6. Meissner- Ochsenknecht Effect pushes out magentic field lines -and keep them out This „diamagnetic“ property is more fundermental than zero resistance

7. BCS - Theory John Bardeen Leon Cooper John Schrieffer Nobel Prize 1972 for theory from 1957 which explained conventional superconductors

8. Different types Type 1: ◦only below critical temperature & critical magnetic field strength ◦changing between states abruptly Type 2: ◦much higher critical fields & could carry higher current densities while remaining superconductivity

9. Applications Strong magnets: ◦MRI, Maglev, LHC, Coilguns,... SQID magnetometer RF and microwave filter Low-loss power cables Electric powered: ◦Motors, generators, transformers

10. Summary Zero resistance Expulsion of magnetic field lines Two different types Cool but very expensive applications Questions ?