Superconductivity Michael Spreitzer Overview Superconductivity Who discovered it
- Slides: 10
Superconductivity Michael Spreitzer
Overview �„Superconductivity“ �Who discovered it ? �Meissner �BCS ? & Ochsenknecht effect? – Theory �Different types of superconductivity �Applications
Superconductivity �Zero resistance �Expulsion of magnetic field lines
Critical temperature � Electrical resistance drops to zero � Materals with a ct arround 120 K can be cooled down with liquid nitrogen (77 K) Material Gallium Aluminum Indium Tin Mercury Lead Niobium La-Ba-Cu-oxide Y-Ba-Cu-oxide Tl-Ba-Cu-oxide Tc 1. 1 K 1. 2 K 3. 4 K 3. 7 K 4. 2 K 7. 2 K 9. 3 K 17. 9 K 92 K 125 K
Heike Kamerlingh Onnes � 1853 -1926 �Dutch physicist �Liquified � 1911 He 1908 (4 K)
Meissner- Ochsenknecht Effect �pushes out magentic field lines -and keep them out This „diamagnetic“ property is more fundermental than zero resistance
BCS - Theory John Bardeen Leon Cooper John Schrieffer Nobel Prize 1972 for theory from 1957 which explained conventional superconductors
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
Applications �Strong magnets: ◦ MRI, Maglev, LHC, Coilguns, . . . �SQID �RF magnetometer and microwave filter �Low-loss power cables �Electric powered: ◦ Motors, generators, transformers
Summary �Zero resistance �Expulsion of magnetic field lines �Two different types �Cool but very expensive applications �Questions ?
