Superconductivity of Iron Fe) re dependence of the Superconductivity 908, Kammerlingh-Onnes experiments on liquid He(a GPa. A 10% drop in resistivity perconductivity at around 1.5 K. Hg resistance: 0.08 ohm 5K to 0.000003 ohm @ 4.2K Shimizuet al Nature 2001. 112316 The temperature dependence of the magnetization 986, G. Bednorz, K. H Muller (BM,. La-Ba-Cu-O Oxide: Te=35K expanded in the upr K. The lower inset shows the disappearance of the Meissner signal in iron when the pressure is decreased to 3.5 GPain the b c.c. phase. in La.0(1986tp Discovery of Superconduct Brief History of Superconductivity b1911 Kamerlingh Onnes discovered superconductivity in Hg b1913 Kamerlingh Onnes won the Nobel Prize in Physics 21953 Superconductivity was reported in V Si at Tc=175K 21972 Bardee, Cooper& Schrieffer won the Nobel Prize 86 Muller and Bednorz (IBM-Zzurich) 21987 Muller and Bednorz won the Nobe forefront of research 1988 Te was pushed to 120K in a ceramic containing Ca and a1993 Hg Ca Cu, Og was found to superconduct at Te=133K 39K Superconductivity in MgB2 Characteristics of Superconductors In MgB, hexa Ing or uI until a force is appley rs., ring continues in centered on the hexagons duced magnetic field ure2001,410,63 exactly opposes the applied field. The material is strongly MgB, like graphite, has strong o bonds in the carbon atoms, not all the a the boron planes has a much stronger effec ate a magnet above the of strong electro surface of the superconductor3 Superconductivity of Iron (Fe) Shimizu et al., Nature 2001, 412, 316 •Temperature dependence of the electrical resistivity of iron at 25 GPa. A 10% drop in resistivity indicates the onset of superconductivity at around 1.5 K. The temperature dependence of the magnetization of iron under pressure obtained by cooling the sample at a magnetic field of 130 G. The signal at 21 GPa (the area enclosed by the dotted line is expanded in the upper inset) shows the appearance of diamagnetism at temperatures below 1.7 K, which is confirmed by the signal given by tin at 2.7 K. The lower inset shows the disappearance of the Meissner signal in iron when the pressure is decreased to 3.5 GPa in the b.c.c. phase. 1908, Kammerlingh-Onnes experiments on liquid He ( a few ml) Hg resistance: 0.08 ohm @ 5K to 0.000003 ohm @ 4.2 K 1986, J. G. Bednorz , K. H. Muller (IBM) La-Ba-Cu-O Oxide: Tc = 35 K Superconductivity Discovery of Superconductivity in La-Ba-Cu-O (1986) “At the extreme forefront of research in superconductivity is the empirical search for new materials.”(1983) Brief History of Superconductivity 1911 Kamerlingh Onnes discovered superconductivity in Hg at Tc=4K 1913 Kamerlingh Onnes won the Nobel Prize in Physics 1933 Meissner and Ochsenfeld discovered the Meissner Effect 1941 Superconductivity was reported in Nb nitride at Tc=16K 1953 Superconductivity was reported in V3Si at Tc=17.5K 1962 Development of first superconducting wire 1972 Bardee, Cooper & Schrieffer won the Nobel Prize in Physics 1986 Müller and Bednorz (IBM-Zurich) discovered High Temperature Superconductivity in La-Ba-Cu-O at Tc=35K ! 1987 Müller and Bednorz won the Nobel Prize in Physics 1987 Superconductivity was found in YBCO copper oxide at Tc=92K !!! 1988 Tcwas pushed to 120K in a ceramic containing Ca and Tl 1993 HgBa2Ca2Cu3O8 was found to superconduct at Tc=133K 39K Superconductivity in MgB2 In MgB2 , hexagonal honeycomb layers of boron atoms alternate with layers of magnesium atoms, centered on the hexagons. MgB2 , like graphite, has strong s bonds in the planes and weak p bonds between them, but since boron atoms have fewer electrons than carbon atoms, not all the s bonds in the boron planes are occupied. And because not all the s bonds are filled, lattice vibration in the boron planes has a much stronger effect, resulting in the formation of strong electron pairs confined to the planes. Nagamatsu et al. Nature 2001, 410, 63 Characteristics of Superconductors Loss of Resistance! ¾¾ Zero electrical resistivity. This means that an electrical current in a superconducting ring continues indefinitely (at least for a very long time ~ years … ), without dissipation through the ring or until a force is applied to oppose the current. MeissnerEffect! ¾¾ Superconductors expel all magnetic flux in a process called the Meissner effect. The magnetic field inside a bulk sample is zero. When a magnetic field is applied, current flows in the outer skin of the material, leading to an induced magnetic field that exactly opposes the applied field. The material is strongly diamagnetic as a result. A superconductor excludes magnetic flux. In this experiment, this is used to levitate a magnet above the surface of the superconductor