Structure of Cuprate Superconductors Cuprate Supero conductors . The Cuprate superconduct . The CuO, layers are responsible for the lI contain a layer with superconducting properties "The other layers serve as sources of electrons -This layer can be planer .The copper 3d and oxygen 2p atomic orbitals perature for significant orbital cuprate superconductors have mixing>band structure. layer structures as well This band is half filled because Cu(n) has a d9 -For example configuration TI2 Ca, Ba CugO . The half-filled band is tuned electronically by the effects of the neighboring layers in the lattice T, vs Number of CuO, Layers Why Do They Superconduct? T株,C In compounds such as Y Ba Cu, O- the metal ion ( i.e But an individual metal ion cannot be partially oxidized. There will be holes'of positive charge(Cu+ ions)within the lattice This type of superconductor is referred to as a p-type Compounds can also be de to insert extra electrons into the lattice (i. e. a reduction), e. g. La, cuOa+ -This is called an n-type superconductor. Why Do They Superconduct? Lanthanum Barium- Copper Oxi One explanation involves the use of holes within the Superconductor electrons travel along the ion planes in the lattic oThis ceramic material As an electron passes a positive hole(due to oxidized cation. was the first of a ner Liy.a, CaOt class of high temperature ductors. It is made by randomly -This is due to electrostatic repulsion. substituting so The oxidized cation(Cu+)then reduces, and the reduced o t le.ps on(Cu+)oxidizes lattice of lanthanum -Effectively, the hole moves backwards (as an electron copperoxide in what is moves forward This“ extra nt that is caused by the normal current is the super7 ßThe Cuprate superconductors all contain a layer with stoichiometry CuO2 . –This layer can be planer ßThe other high-temperature cuprate superconductors have layer structures as well. –For example: Tl2Ca2Ba2Cu3O10 Structure of Cuprate Superconductors Cuprate Superconductors ßThe CuO2 layers are responsible for the superconducting properties. ßThe other layers serve as sources of electrons. ßThe copper 3d and oxygen 2p atomic orbitals are close enough to allow for significant orbital mixing ‡ band structure. –This band is half filled because Cu(II) has a d9 configuration ßThe half-filled band is tuned electronically by the effects of the neighboring layers in the lattice. Tc vs Number of CuO2 Layers Why Do They Superconduct? ßIn compounds such as YBa 2Cu3O7-x the metal ion (i.e. copper) is partially oxidized. ßBut an individual metal ion cannot be ‘partially’oxidized. –Instead, the lattice will be comprised of a ratio of Cu2+ to Cu3+ ions, depending on x. –There will be ‘holes' of positive charge (Cu3+ ions) within the lattice. –This type of superconductor is referred to as a p-type superconductor ßCompounds can also be doped to insert extra electrons into the lattice (i.e. a reduction), e.g. La2CuO4+x –This is called an n-type superconductor. Why Do They Superconduct? One explanation involves the use of holes within the superconductor. ßWhen a current is applied to the superconductor, the electrons travel along the ion planes in the lattice. ßAs an electron passes a positive hole (due to oxidized cation, Cu3+) in a neighboring plane, it will push negative charge from orbitals on a reduced cation (such as Cu2+) towards the hole. –This is due to electrostatic repulsion. ßThe oxidized cation (Cu3+) then reduces, and the reduced ion (Cu2+) oxidizes –Effectively, the hole moves backwards (as an electron moves forwards). –This “extra”current that is caused by the normal current is the supercurrent. Lanthanum-Barium-Copper Oxide Superconductor This ceramic material was the first of a new class of high temperature superconductors. It is made by randomly substituting some barium atoms into the lattice of lanthanum￾copper-oxide in what is termed a solid solution